Mmm well my boyfriend brought me to events when we were talking but when he did, he would introduce me with my name and when his guy friends would ask, he would tell them our status as a way of being a "gentleman" since he was pursuing me. And your friends should already have a good idea of who she is (you have been tellin them a bit about her, right?)
Either one of the first 2
Don't say the third one, it makes it sound like you're just friends. You've actually placed them in order. The first one is probably the best.