Hahaha seriously i would try to advice her and help her out, find out why me and convince her it's not right. If that means finding her a boy then fuck it, i will
Yeah man 13 is pretty fucking young to be obsessed with you.. you should invite her somewhere where you guys can talk and just tell her whats up. Tell her you are just too old and the age difference is just way too much. If she starts to act all crazy tell her you will have to block her on facebook. Just get it through her little head that is could never work...until she is 21 and you are in your 30's
Best thing u can do is introduce her to someone u also know is 13. Make him look cool and tell her cool stuff a 13 year old would do to her. If all else fails. Just fuck the little turd nugget. Lol just kidding. That's gonna make things 100000xs worse.
Rape her whilst wearing a mask, comfort her emotionally after until you become a father figure to her and she has no more sexual interest in you.
Just tell her that you're too old. Is this seriously a difficult situation? Tell her if she doesn't let up you'll have to delete her because it makes you look like a pedobear.