My upcoming dilemma

My nephew's wife, AKA my niece, is having a baby shower in about 3 weeks. Important to note that we don't consider each and other 'in-laws'. You marry in to my family, you BECOME my family. Thus says the Family Matriarch. My brother's ex wife will be here (they are best of friends) and she's been invited, too. Last year her current husband was here, twice, to visit and HE is also considered family.

My dilemma has to do with another individua I suspect will be invited. My former brother in law's girlfriend. She was his girlfriend before he met my sister. My sister really didn't like her OR her family. Not a jealousy dislike, but a dislike based on the face that this female is just not a good person. She's done her best to alienate my former brother in law from both his kids AND extended family. She also erased every trace of my sister from the house. I can't even go there, anymore.

The last time I saw here was in 2018, at my niece's wedding. I was pretty emotion, feeing extreme guilt about doing everything my sister should have been doing.. This female came up to me and said God took my sister so that I could be there for her kids. OK, I was already DEEP in survivor guilt (still am) and the only thing I wanted to do was to knock her off of her feet. Preferably in to a mud puddle. From that point on, I have excluded her from al family celebrations, resulting in y former brother in law not attending. Fitting because she once pressured my FBIL to disinvite my brother from a party.

They broke up for a while and thing were almost back to normal. Everyone was happy and nobody worried about the 'mother superior' admonishing them for having fun. My family does have a great time when we get together. Now that she's back, we're back to alienation.

Anyway, as to the shower. I just don't know how I will handle being in the same room with her. My bestie and my niece have promised to intercept her. Honestly, I don't even want to see her face. I might take a double dose of 'chill pill' before I leave for the house.

I am SO EXCITED about the prospect of being a grand auntie to a beautiful little boy. I have a grand niece but rarely see her. (I've been disowned by her other. Not sure how because I have zero connection to her family.) The idea that there will be a little soul for me to sing to and tell stories about Dragons and Knights is so exciting.

ANYWHOO, any suggestions as to how to react should this female approach me? She's been so disrespectful and caused so much damage to my family, I might just respond to her in Welsh, French or Spanish and then escape her presence.

Sorry this is so long but it's really driving my anxiety.