well she may not be ready to talk about it yet it may be embaressing. so just give her signs let her know that she can trust you and you dont know how long it will take but if you really care about this girl you'll give her space and just give her time and maybe later on she will wanna be more than friends and then maybe tell you about her past. But if she doesn't want to then dont push her to make her tell you if she doesnt wanna then dont presure her!