oh that is unfortunate that you work in the same place, ouch.

Remember that it is likely as uncomfortable for her as it is for you. That knowledge might help.

Would it help to raise the issue with a supervisor? There have been times I've had to get involved.

What about communication with her? Are you two able to talk at all? Are you comfortable then letting her know your own expectations for keeping this out of the workplace?

What a can of worms my friend, my thoughts are with you. This can't possibly be any fun at all.