FX understands that finding out that a friend has feelings for you can be a real surprise, and it’s ok to be a little bit uncomfortable about it at first.  This can happen even if the friend is of the opposite sex, or of the same sex as you described, because it changes the overall dynamic of what used to be just a friendship.  However, ignoring your friend isn’t really the right thing to do, even though it might seem like it.  You are probably hurting her feelings by doing this, and despite her possible romantic feelings for you, she’s still your friend.  Also you didn’t tell FX how you found out that your friend likes you, but keep in mind that rumors can start and be spread very easily, and you probably don’t want to lose a friend because of something that might not even be true.

That being said, you should keep in mind that at age 13 and throughout most of the teenage years, most people are just beginning to explore their sexuality, sexual identity and sexual preferences.  They are learning what and whom they like and don’t like, and this is all a natural part of growing up.  It’s completely normal to have fantasies about members of the same sex, and it doesn’t mean that someone is gay, lesbian, or bisexual.  It simply means that they have some sort of attraction to another person, and that is completely ok.  And, it’s important to remember that sexual preference is something that is biological and predetermined, which means that whichever sex people have relationships with is something that they don’t have a choice about- people’s bodies simply find certain things attractive.  

The best way to deal with this depends a lot on what type of relationship you are comfortable having with this friend.  If she is a good friend and you don’t want to lose her, and if she has personally made her crush clear to you, then it might be a good idea to tell her that while you don’t share her romantic interests, you do value her friendship and would like to continue to be friends.  If you’re friends in the first place, you probably like doing similar things and having fun together, and this shouldn’t have to change.  However, if she makes you uncomfortable by her actions, then you need to tell her this, and if they continue, then perhaps the best solution will be taking some time away from her.  It’s unfortunate to spend less time with a friend, but you shouldn’t stay in a situation that you’re not comfortable in.  Hopefully, if you’re both honest about your feelings and comfort levels with everything, you two can remain friends.