hmm this is tough, you just fell for the girl and it didnt work, thats the fact.at the moment 'thanks to' the whole situation you blame yourself that it was all your fault which it isn't true.people can't decide about their feelings so you couldn't predict that u will be 'in love' with her and that she won't feel same.as u wrote in your post the girl probably still feels somethig serious for her ex bf.i wouldn't advise you keeping her as a friend because u can suffer even though u don't realise it.to me it might make things even worse, probably u would start to feed yourself with afalse hope.i think she just needs a male friend who will give her some support but u cant be the one, i really think that u can't make friends with a person you are attracted to.what if one day you will see her with another man and according to what she said before about not hurtin you she will do that even not intentionally,eh?won't you call spending time with the girl as a waste of time?i bet you will...she ain't the only girl in this world and you are too young to put yourself down like that.life is too short to have sorrows, just try to live your life the best you can, it ain't easy but we have to fight and never give up...