What is it with her? And what should I do?

Even if you did manage to sort it out with this girl there is still going to be her nasty friends there and they will be telling this girl to dump you and stuff and they will do anything to make that happen and eventually she will listen, and also you see that she said you strain her life well think about it she is actually straining yours and ye you might feel for her but there's other people and as for your problem with other people like you said, there's no mature people when they have decided to mature a bit then things would be alright but personally I say talk to this girl and just explain that you do love her but your happy to be friends and don't listen to her frends they seem reli nasty to me....