Does anyone have any idea whats up?

Ok so today this girl who is very pretty gave me a REALLY dirty look.Im not even kidding if looks could kill I would be in my casket by now. She looked at me like I just kissed her boyfriend. I've never met this girl in my life. Idk y she was even at my school.I was just walking past her with my friends. I wouldn't be so confused about this but, this isn't the first time. I've been given a lot of dirty looks this year. I havent said anything to them. I dont dress like a skank or anything. Why do I keep getting dirty looks from other girls?