TIme Lapse Lifeline

Do you sometimes ever get that uncomfortable feeling that someone doesn't really like you, even though you haven't done anything to them.... or nothing you know of? At uni there's this girl I've spoken to a couple of times over the year so far, and everything was alright until the start of this semester. Maybe it's the insecurities I have, but every time I see her now, I get the distinct feeling she isn't happy to see me and that she brushes me off. I've asked a friend about it, and she says it's 'just me' and it's all in my head. I guess it could just be me being paranoid, but I can't shake off the feeling I've done something wrong.