I understand why you left the bar, if you felt that was best for you, good job doing it. You just have to specify that so nobody thinks your trying to say that somebody else is responsible for your feelings and actions.
Yes, she doesn't have to meet you and you can't force her. It might feel like she's being disrespectful to you, but she is being respectful to herself, just as you were being respectful to yourself when you suggested meeting in the first place. If you can't respect and take care of yourself, it's unlikely you'll be able to do either for anybody else.
Lastly, while this could just be an insecurity that you need to work through, it could also be a new boundary for you. You're bound to have a few come and go over the years, as you grow and develop. Though they can often cause problems/drama if you discover one in the middle of a relationship because it will feel like you're changing the rules in the middle of the game.
Example: There are a large number of people that use the term fluid bonding, which is an agreement to have unprotected sex within the fluid bonded relationship and protected sex outside of the relationship. People that ask for this agreement have a boundary about safe sex and look for partners that either respect that boundary or share it, and we subsequently call it an agreement.
My personal boundary is to meet anyone my partners have sex with, within geographical reason that is. I assume Beth and Mary are sexually active, I doubt however, that they are using dental dams, gloves, condoms on toys, or separate toys. Suffice it to say I am super STD/STI conscientious, if I were in your place I'd be freaking the fuck out, but that's just me. I haven't always had this boundary, and was once quite unsafe, but I can only be in a relationship with people that respect my boundaries.
Shhhh!!! Be vewy vewy quiet. I'm hunting wabbits. I mean unicown wabbits.