Girls and boyfriends?

I said this before and I know not all girls are open books. So I try talking to this girl at school. She's cool and all and discrete. She seems to lied at little, I observed her and seen how she talks just to see how she was, a couple of dudes in my table were talking to her like asking were she works, what cles she takes, or how come she wasn't in cl that day. I think that its a very good umption that she has a boyfriend or seeing someone that's why she's being like this. The guys are still hitting on her I gave up on her a while back ago cause I knew I wasn't financially available and had nothing in common. We been in cl for 4 months already. But my question is, are some girls afraid to admit they have a boyfriend and if so do some girls do this to lead some guys even though some don't have a chance. If you read this far thanks, if you have a similar story I would love to hear it.