How do you stay unbothered around a woman who repeatedly crosses boundaries to assert dominance?

I’m in a group where there’s a girl who openly seeks male validation and repeatedly crosses boundaries—hugging guys tightly, sitting on laps/shoulders, getting overly touchy, and flirting very obviously, even with men who are taken or emotionally connected to someone else.

This happened with my ex as well. What hurt wasn’t just the flirting, but how deliberately it was done in front of me, almost to assert dominance or put me down. I don’t engage with her, I don’t compete, and I don’t want drama—but being around it is still uncomfortable especially being touchy with my ex(I don't want my ex back but it sucks to see that the reason of our break up and it's still happening)

I’m trying to handle this with self-respect and dignity, not confrontation.

How do you:

stay calm and unbothered in the moment?

Create your own aura or intimidating presence that will ensure she doesn't do it again or atleast grab others attention that she is doing it again

not let it ruin your entire day afterward?

emotionally detach when you can’t avoid the group?

Basically how to handle such mean girl/emotional bully scenarios??

Looking for practical advice, not validation or drama

Also leaving the group is not an option for me unfortunately Atleast for a year or 2 I have to stick in