How to Deal With Your Boyfriend's Female Friend
To deal with your boyfriend's female friend, give her a chance and spend some time with the two of them to see what their relationship is like. If your boyfriend treats you differently around her, there could be a problem. However, if you enjoy hanging out with two of them and you don't get bad vibes, don't stress about it. Just try not to act jealous or passive aggressive about the situation. If you don't think you can trust your boyfriend, or if you think he's acting suspicious, then you may want to call off the relationship.
Join in on some of their activities together. Having a chance to see if his treatment of you changes when she is around can go a long way in making sure they are just friends. If your boyfriend suddenly won't show you affection when the three of you are together, there probably is a problem. If they are really just friends, both your boyfriend and his friend should show you respect. If you can hang out with the two of them and not get any bad vibes, chances are, they are just friends and you have nothing to worry about. Get to know his friend better. If you have concerns about her intentions, it might make you feel better to spend some time with them together and with her on your own. Perhaps spending more time with her can help you to see that your concerns were not warranted. When the two of you spend time together, try to view her from your boyfriend's eyes. Does she have a fun personality? Does she tell great jokes? Is she a great listener? Give her the benefit of the doubt and don't immediately look for flaws. If there's nothing more to their relationship, she should have no problem getting to know you better. It's a red flag if she seems jealous because you two have very different roles in his life. Don't be passive aggressive about their relationship. If you have trouble accepting their friendship, you may need to check yourself. Passive-aggression can be demonstrated when you are afraid to speak your mind or wary of being honest. You may not listen when your boyfriend talks about his female friend. Or, you may plan his birthday party and "forget" to invite her. Passive aggression may serve your purposes, but it can also destroy your relationship. If you notice yourself doing these things, ask yourself how you can have your thoughts and needs met in a more adaptive way. Write down your concerns before approaching your boyfriend. This step will help you organize your thoughts. Writing down your issues about concerns will help you stay focused and not react in an overly emotional way. You want him to hear your concerns not just that you are crying or yelling. Focus on specific behaviors or events that are red flags for you. This may include things like late night phone calls, your boyfriend taking special time to make himself look nice before he sees her or him seeming to hide things from you. Talk it over with an impartial person like a sibling or friend. See if this person agrees with your need to worry. For example, it may not be much to worry about if they live across the country from one another and only see each other on occasion versus hanging out daily. You may find this outside person may have insight you missed, and it will help to clarify if you are seeing real problems or just worrying over nothing. This conversation will also give you practice talking things over so you are prepared when it comes time to have the conversation with your boyfriend if it seems like it is needed. Taking the time to reach out for another opinion also gives you a bit of time between an event that might be triggering this conversation and sitting down with the boyfriend. Generally, it is best to give yourself at least 24 hours after a stressful event to calm down and prepare for a sit-down conversation. Approach your boyfriend in a non-threatening way. Don't say “we need to talk…” which could put him on the defensive that there's a problem. Casually bring up the subject when you are driving or doing some activity together. Guys may be intimidated by discussions that require excessive eye contact. Sit beside him and try to be non-confrontational. Start off with a casual conversation to gauge how he feels about the situation. If he is suddenly defensive about things or is overly protective of the friend this may mean there are bigger issues. The focus of the conversation should be about the two of you and not dominated by him standing his ground as far as spending time with her alone. If you are spending the whole conversation talking about why he needs to see her or why she really needs him, there are possibly deeper feelings there. Explain your worries by using “I” statements. Be specific. Maybe you think he doesn't see it but she's into him. Or, maybe you feel like they spend more time together than he and you. Make your concerns clear. Owning your feelings will help guide the conversation to what you need from the relationship and away from her. Examples of “I” statements may be: “I feel left out when you and Jill do activities we talked about doing together because it seems like you didn't want me there.” “I feel sad when you cancel plans with me and end up hanging out with her because it looks like she is more fun than I am.” “I feel angry when I see posts of line of pictures of the two of you because our friends ask why you are posing like that with her.” Try not to be upset if he brushes it off. If he is really not into her, this may be his way to move past the conversation. In some cases he may not be the one who is actually reaching out to see her. There is a chance she actually wants more and is the one making efforts he may in fact not see. Give him time to think over his relationship with her on his own. Making him aware of some red flags tied to how she behaves may also make him more aware that his friend may have underlying feelings for him he may not have considered. For example, if she calls and he lets it go to voicemail when you are together, does she suddenly blow up his phone until he answers? This could be a red flag that it's her and not him. Have a talk about cheating. What do both of you classify as an indiscretion? Men and women often have very different visions of what counts as cheating. Men focus on the actual act of sex while women also include things like flirting and emotional closeness as a form of cheating. Agreeing on a definition of cheating for your relationship will serve as a benchmark for behaviors and things that are not OK. Make sure to be as clear as possible as far as things you do not see as being within a friendship with the opposite gender. Figure out where you stand in the relationship. Are you exclusive? Or, would your boyfriend think it is okay to date another girl? Making sure you are on the same page will help to clarify if there is in fact another relationship happening at the same time with the female friend. If you two decide together you are exclusive this needs to be communicated with the female friend to make sure she is getting the same information you are. Set some guidelines that make you feel more comfortable. Perhaps, you would prefer if they didn't hang out alone. If your boyfriend seems unwilling to negotiate these guidelines, there may be more to the relationship than he is admitting to. If he is truly not interested in this friend he should be open to only doing things you are OK with. Things to consider would include how often they see each other, if they spend time alone and how he deals with phone calls or texts while you are together. Turn the tables. See if your boyfriend would be OK if you had male friends. Maybe he just doesn't fully understand your envy. Bring up the topic and see what he says. This is not retaliation, so you shouldn't go out and find someone to make him feel jealous. It's meant to help him consider things from your perspective. Remember that trust is an important aspect of a healthy relationship. A big part of trust is respecting your partner and not hiding things from him or her. It's also largely dependent on believing the best in one another. Finding out that your boyfriend is hiding details about the friendship with a female can be a sign that there is more going on. Explain to him that it jeopardizes your trust when he hides things. However, it's also important to believe that he will be faithful to you. Unless he has been giving you clear signs that something more is going on, try not to make an issue where there isn't one. Break it off. Yes, you should trust your partner. However, if you cannot shake the feeling that something is going on between them, you may want to follow your instincts. If there relationship makes you feel uncomfortable and your boyfriend refuses to get some distance, you may have to go your separate ways. You may also need to leave the relationship if you can't seem to overcome your jealousy and accept their friendship. Perhaps you simply can't deal with "sharing" his time with another person. You will need to examine your expectations--and maybe talk with a counselor--before you can be in a trusting romantic relationship. 
Join in on some of their activities together. Get to know his friend better. Don't be passive aggressive about their relationship. Write down your concerns before approaching your boyfriend. Talk it over with an impartial person like a sibling or friend. Approach your boyfriend in a non-threatening way. Explain your worries by using “I” statements. Try not to be upset if he brushes it off. Have a talk about cheating. Figure out where you stand in the relationship. Set some guidelines that make you feel more comfortable. Turn the tables. Remember that trust is an important aspect of a healthy relationship. Break it off. 