Ended up having drinks with 2 female co-workers and the girl from work I've been seeing. She has also brought along her lapdog guy.

This is the guy that frequently picks up her and drops her off (she doesn't have a car) and generally bends over backwards to accommodate her. I haven't inquired as to the extent of their physical relationship since I don't want to look jealous, but she's said they've tried dating and it hasn't worked out and she feels like he tries to pressure her into an exclusive thing. I'm not sure why he still hangs around, but ehhh, it saves me from having to worry about carting her all over the place.
At any rate, they end up in a booth at the bar, and I pull up a chair at the end of the booth. For at least half an hour straight before she leaves, my chick from work is playing footsie with me under the table.....wrapping her leg around mine as I slide my foot up her leg.....occasionally reaching under the table to rub my calf, feigning as if she's adjusting her sock or something. All the while we're doing our best to maintain composure and keep up several cross table conversations. It becomes a really fun game of skirting the line, since both her lapdog and our mutual co-workers are present. I don't think anyone noticed.
Eventually she and lapdog go to the bar and tab out. I glance over and notice him trying to lean in closer and slide his arm around her waist. I think, "Sucker." Then I reconsider for a moment - maybe I'm the sucker. Or maybe we're both suckers :lol Oh well.
She hugs everyone as she's leaving.....when I get a hug leans for a quick kiss on the lips. She gets distracted for a couple minutes and does another round of goodbyes. I get another hug, another kiss. This is a much less fun kind of skirting the line, since it's completely out in the open for anyone to see. It was loud and crowded with everyone talking to someone else, so I actually am not sure if anyone saw anything. I know a friend of mine from outside work was there with another group and he gave me a look after it happened.
I still get the sense that this will not end well, but it's certainly fun for the time being. For once I get to be the asshole that the girl screws around with while some other poor guy completely kisses her ass and gets zero respect for it.