Ouch!

This could get so messy for you. It will only get worse. She clearly has no qualms about pulling you into her mess. All that will happen is that they will both ultimately turn on you in their frustration and anger with each other.

What is it that makes you reluctant to just close this relatively new relationship down?

You’ve told her that you are extremely unhappy with what she has said to her partner. Just don’t answer her calls and messages. Tell her you need some time to think things through, and that you’re not happy about how she has involved you in her mess, and then just stay away.

Jeff.