KiltedBishop and Casey both made very astute observations. Trouble is I agree with both of them.

Yiou definitely have the poopie end of the stick.

I also agree that you should have a discussion with your supervisor and ask him to invite Mary and her supervisor to join you.

Show that you are willing to discuss the situation and that Mary is the one who is being disruptive. Also be sure to use the word harrassment, but don't threaten a lawsuit. At least not yet.

Best of Luck.