Is she cheating on me?

My girlfriend of 3 months hasn't been wanting to hang out for the past 3 weeks (she lives close enough to commute to college so she lives at home, I live on campus). Recently she has been coming up with bleak and circumstantial reasons why she cant hangout like " I haven't had a day to myself in months". If we are free at the same time she wont want to drive 20 minutes to come over. Anytime she IS over she sets an alarm to remind herself to leave before it gets too late, and while that was understandable at first, she has been setting less and less time lately, the last time I got her to hang out was over a week ago and that was only for 30 minutes and only because it was after class. Recently its been taking her forever to reply to texts and its never anything I can respond to, Just "hahahaha" or "you're such a dork ;)"

I have a hunch that she may be cheating on me. She shaved her legs the other day for the first time in over 6 months when she told me she wouldn't shave. I have not seen her since she shaved so it wasn't for me.

Although, it is finals week at school and she has been studying and working hard lately to get **** done, so I assumed she has been neglecting me because she is lost in her books. She didn't even want to go on a 15 min walk for a study break. she is very passionate about her schoolwork, she puts school first. I hope I'm over reacting and I am just being paranoid ***** because this is my first serious relationship and I don't want to lose her.