CM...seriously, how many 14 year olds marry their boyfriend/girlfriend. More to the point, how many 13, 12, 11 year olds marry their boyfriend/girlfriend. She "cheated" on her past boyfriends? No...that's simply ridiculous, because 11, 12, 13 year old's can't (shouldn't!) have relationships so serious that anybody can be considered to have cheated. If I recall correctly, she isn't allowed to even "date" you alone -- so how is she going to "cheat" on anyone when she is never alone with anyone?
Here's the deal...she's 14...she's not supposed to be in "committed" relationships, because she hardly knows who she is herself, let alone what she is looking for in a mate.
Just hang out, have fun, flirt with her....but leave it at that, man. If you are destined to be botyfriend/girlfriend, it will come when it's ready....sounds like you went from "hardly talked" to "I'm in love" in about 2 seconds flat. Cool your jets, Pancho...there's time enough for love when the two of you grow up and figure out who you are.