Is OTHER wrong in the post ? POST : For lack of a better term, she’s not my ex, but we dated exclusively for 3 months. And we’ll call her Sadie. Sadie ended things with me a week ago citing that she didn’t have time for a relationship and also felt very cynical about them. Sadie wanted to remain friends. We are supposed to go to my close friend’s NYE party. To be clear it’s his house. I’ve been close friends with the host for 8 years. Sadie’s been friends with him for 2 months and got his contact info at the host’s Birthday party two months ago that we went to together as each other’s dates. My friend group will be there. Sadie’s won’t. The only person she shares a mutual friend with in my friend group is her step sister. We were supposed to go together as each other’s dates well over a month in advanced until she ended things. Today she warned me that she would be bringing her new guy she’s been dating the past week as her date. I was confused since she said she didn’t have time for a relationship; didn’t believe in relationships and love. Sadie told me she met him the day before she decided to end things with me. Sadie has gone on several dates with him over the course of the week and intends on bringing her new guy to the party as her date. I told her that I’m not okay with this. Although I’m upset she’s dating someone else, that she ended things with me for someone else, and completely went back on the reasons she didn’t want a relationship, she’s well within her right to date whomever and whenever she wants. I made this clear multiple times. But I don’t want her date at the party. We got in a huge argument about how she feels I’m being unfair. But I told her I don’t care who she’s dating, I just don’t want to see it because it’s hurtful and unfair to me. That her bringing this guy to my friend group’s party is extremely inconsiderate of my feelings. I told Sadie that she knows I still have feelings for her, and seeing her with another guy only a week after she ended things is hurtful and painful to me. Especially since she replaced me with him and was supposed to be my date to the party. And if the roles were reversed, I wouldn’t be doing what she was. I made it clear that if it was her friend group hosting, she’d be well within her right to bring whoever as a date. But Sadie’s bringing this new guy into my friend group. This is my friend group. Not hers. And that she’s overstepping her boundaries. I think that out of respect for me and my feelings, and the fact that she’s coming to my friend group, and not hers, she shouldn’t bring the guy she left me for. And if she wants to do something with the guy, that’s perfectly fine, but she should do it with her own friend group and make her own plans. The date and two additional friends she’s bringing weren’t even invited on the Facebook group for the party and aren’t on the guest list. Sadie is. Although when the host gets drunk he’s not concerned with who comes. She wouldn’t be going to this party if I didn’t suggest us going together months ago. She usually does NYE with her friend group. So AITA? 

TLDR: Ex ended things last week. Is dating someone new despite breaking up with me because she has no time for a relationship. Wants to bring her new guy to a NYE party we’re both going to where we were supposed to be each other’s dates. I’m not okay with it. Party hosted by my friend group. Not hers. New guy isn’t on the invite list. 