Maybe your boss will address it if it’s just only you 2 ?? do you know if more people are going??? If so I’d just stay busy chatting with nice adult people and not her.

I have done both ends ... I was overly nice and it gagged me to be overly pleasant but worth it because she always looked like an irrational idiot

And

I have told someone point blank in a normal level voice that I am absolutely done with Jr high nonsense.. we are both adults and You will start acting like one because I’ve had enough, and if one more thing happened I would go to HR.

Both worked for me. I don’t know why people have to act nasty and mean. Life is too short

Hope she backs off ASAP