How important it is to be friend or fake friendship with ur boss?

My boss has created a pretty casual work environment, we work like hell but its pretty casual. I've always tried to keep up this very polite, quiet, professional persona, sometimes I think she'd like me to talk more, but she doesn't dislike me, I mean if you do the work, come in when you're supposed to, and don't give them any trouble I don't see how they can complain.