Honestly, I think you might need a different group. I hate to say that, but there are lots of perfectly nice people out there who don't accept me for who I am. As long as they don't, I can't be myself with them, and the result is that they're never going to be real friends whom I can depend on.
So you have a choice: 1) keep up this superficial relationship where you are, indeed, mostly a silent observer, biting her tongue and putting up with comments that frustrate and perhaps even offend you, 2) stand up to them and make an issue of the GT thing to let them know how you really feel, risking your position in the group with the conflict, or 3) find another group.
Which you choose is pretty much solely dependent upon your personality and how likely you are to find a better match.
I can tell you that I spent several years in a pre-K playgroup with women that sound a lot like the ones you describe. I kept my mouth shut and survived it, but I was really desperate to find a place where I fit in by the end of that time. It did not leave me feeling whole and complete. It left me feeling stifled and frustrated.
Of course, you have this forum, and at the time I had nothing of the sort. Maybe you can pour all that out here and keep your polite smile in place there? Maybe? Or are you not that desperate? (I was pretty desperate for adult conversation of any sort at the time...)
I dunno if I'm helping.
Regardless, I've been where you are, and it's just no fun.
I really do sympathize with you.
