Have him distract her

Your plan didn't come out of nowhere. You know your newly found accomplice for quite some time know and you learned pretty fast that he is quite good at smalltalk. This made him fairly popular among the bar staff even if it wasn't quite as popular as he would have liked it. In this case, this ability might turn out to be pretty useful though. He waits until everyone else is gone to start chatting with the girl. It doesn't take long and they're in the middle of a conversation which is exactly what you were waiting for. So far you've hidden in the back to avoid distracting her, now you step behind her and put your fingers on her neck. She flinches instinctively but then realizes that you're just massaging her and relaxes. A few seconds later and she's in the middle of a conversation again. You continue to massage her neck carefully to not distract her from the conversation too much. A bit surprised that your plan is actually working quite well so far, you start to wonder when the appropriate time would be to go a bit further.