It seems like you've done a great job of letting things just kinda happen. A lot of times we humans think too much about what's right, wrong, or indifferent. Why is she uncomfortable with you being intimate with her gf? Especially if there isn't necessarily a sexual element. I know it may seem a bit harsh, but what's good for the goose should be good for the gander.
With that said, again, let me reiterate, you've done a good job of letting things happen as they may. That may be the best course of action for you and as always, keep VERY open lines of communication with your wife.
Live life to the fullest 'cause you never know if you're gonna wake up tomorrow!