I have a big problem with this girl im friends with?

I used to kind of be friends with this girl. Im not trying to sound mean but she doesn't have many friends and is kind of an outcast in school. We started talking one day and she sat with me and my friends at lunch one day. Recently, she told me about these kids from other towns. Just because she told me and out of curiosity I added them as a friend on facebook. Now this is very stupid but...she ims me saying I have no life and that its creepy to add people shes friends with that I don't know. Then she just going on and on and said some things to me that were kind of mean. I just told her that this should not be affecting her and all she did was telling again Im stupid, shouldn't add them etc. So finally I said "look i dont like having enemies, especially over stupid things like this." I tried everything I could working it out with her, and all she did was come back with more fighting. I eventually just said bye. What should I do? What do you think of her and this, isn't it stupid, like I said?