My gf sometimes acts like a guy.. why does she do this!!?

So pretty much sometimes she has the emotions of a guy and says and does things that guys do.. And i don't mean in a butch way.. She has a certain shane likeness (from the l word) and she doesn't understand why i'm mad at her when i get mad.. She doesn't see it at all she thinks its normal, i just wanna know if i should be worried or if i'm just being a nutcase about the situation...