If she makes it clear that she only wants to be your friend, think about if you are okay with accepting that role in her life. If you think staying close to her and watching her possibly date other guys (and maybe even ask your advice about them) would be too painful, it's okay to say so. But if you think you can put your romantic feelings aside, be glad this rad girl wants you in her life and make the most of your friendship.  Don't stick around hoping she might change her mind. It's not fair to either of you if you are secretly hoping she'll fall for you if you do enough nice things for her. You'll be deceiving her and you'll be making yourself miserable. If you are spending all your energy trying to convince her that you're the right person for her, you may be missing out on other girls that would love to date you. You may agonize over why she doesn't like you back, and you may want to ask her to explain it to you, or convince her that she's wrong, or tell her friends to tell her you'd make an amazing couple... but you should probably cool it. If you keep pursuing her when she's not interested, you may start to annoy her or even scare her. You don't need to completely ignore her or be mean. Just take a few steps back and treat her more like an acquaintance. Just like you can't help having a crush on her, she can't force herself to have feelings for you. And while it definitely hurts, it's not the end of the world. It's completely okay to feel upset and sad when something doesn't work out. Luckily, she's not the only girl out there, and it probably won't be long until you meet someone new. Chances are the girl just thought she was treating you like a friend and wasn't trying to lead you on. Try not to hold a grudge and just move forward.
Decide if you can just be her friend. Give her some space. Accept it and move on.