I would be careful of this generalization that "you belonged to her".
Here's why: I have heard, ad infinitum that when men walk up to a couple that men speak to men first because of "male dominance" or that the addressing male is speaking to the leader. It's crap. I don't go up to some strange couple and start addressing the female first because it can easily be taken as me chatting up some dude's GF.
A few years back (2006 if I am not mistaken) some lesbian writer set out to spend a year as a man, and did so. Many of her feminist truisms, such as the males speaking to males first because of [whatever / patriarchy] were debunked by her year as a man.
She had another that when pass each other on the street and make eye contact that it was some test, machismo dominance thing, or whatever. She found that it was purely recognition and by NOT doing it she was seen as shady.
In the same way I suspect, but do not know, that the females who thought you were WITH the woman you walked in with did not want to ignore the female customer and be seen as chatting up / flirting with you.
Just a thought.
Steven