Why do you feel the need to meet Mary? I'm curious if it's because that's what you read should happen or if you really want to. It sounds like there may be other underlying issues that you want to work out aside from jealousy.
I haven't met Karma's girlfriend Cookie. I'd like to...maybe...one day. And she feels the same. And to be honest so far it's worked out really well. Not knowing eachother has made it easier to keep the relationships seperate. I'm not sure how Karma feels about it, but it makes things a hell of a lot easier for me. But I don't have jealousy about her or their time together. I do get angry when Karma doesn't balance time well, but that's a balance thing and not a jealousy thing.
Can you move on and past your jealousy over their time together without meeting her? I get wanting to meet her and clear things up, but if shes not willing why push it?
As for the bar. You know what you are willing to deal with and not willing. Had it been me, I'd have enjoyed my night out and gone about my night whether she was there or not. Nothing said you had to talk to her. Nothing says she and Beth would have stayed upon realising you were at the same place. But it sounds like you were given the heads up, which makes me question if Beth knew you were there, why didn't she go ahead and make arrangements to go somewhere else?