Okay, so I'm not a therapist and I'll be careful not to make any diagnoses here. Please don't take this as a personal attack, but to me everything I read here sounds more like the problem is with you. Yes, what she is doing is not okay, but....
You seem extremely insecure and apparently not able to stand up for yourself. You worry extremely much about what others think of you and let others cross your boundaries. Just the fact that you actually changed your clothes just because she made a comment says more about you than it does about her.
Like I said, you are a grown woman who has children of her own. To blame others or make excuses and hope that someone else will stand up for you now is not only very immature but also sets a bad example. Work on yourself, on your charisma and your self-worth. You don't have to pretend or be mean to be taken seriously and respected.
There will always be such people and you will not change most of them, so either you learn to deal with it or you just endure it. As I said, it's not school or kindergarten. Some conflicts you have to try to resolve yourself as an adult. And if you say that this is not your thing, then you have to learn it.

The interesting thing is that it is mostly women who try to drag others into their conflicts and seem to be looking for something like allies. Not that men are significantly better at resolving conflicts, but they cause less drama.