Do you think this girl has a mental disorder?

It sounds like she is just extremely socially awkward, however I know a girl in my school who is sort of the same way, and I am pretty sure she has Aspergurs (I can't spell it, but you know what I mean). I worked with a special needs child in a theutic horseback riding program who had it, and the girl at my school showed very similar characteristics. Just ignore her and don't listen to what she says. She will eventually learn that she needs to act politely and considerately to people if she wants to make and keep friends. Good luck to you!