Long story short, my former manager, but current coworker's, poor treatment resulted in me developing a case of PTSD. I was diagnosed about two months ago. However, we don't have an HR team so there is no one to disclose to or deal with her bullying behavior (the boss doesn't care as long as she is doing OK work), and leaving isn't an option right now, so I have to grin and bear working with my abuser. Luckily, she works in a different department so we only really interact during morning meetings.

I am holding a 4th of July at my house for all of my interns. Her interns are not invited since they work in a separate office from us.

My boss knows about the party, but he will not be attending. I have not told her about it, but I know she will find out about it and invite herself and her interns so she can take credit.

How do I politely tell her that she isn't allowed in my home?

Letting her in is not an option and will trigger a PTSD episode.