Can’t deal with a petty ex-friend

I had a kind of intense and dramatic friend break up with my (now former) friend a couple of years ago, after one of our other friends unexpectedly passed. Of course we were both in a bad place, and I eventually told her it was too much for me to sustain petty fighting and her relentless passive aggressive and judgy comments. At first it was whatever but when it became targeted about our friends death and how we were dealing with it differently I think she crossed a line. Imo she’s just still very immature (despite being almost 40 years old) and has never really healed from her past friend break ups and a lot of other trauma, and so simply cannot take accountability for anything at all. I sent her a sweet msg at the end wishing her well but saying the friendship was taking a toll on me. And she replied saying she will always hate me or something.

Anyway, in the years since, I’ve moved on and healed and spent time focusing on my true and close friendships. I’ve truly barely thought about her in years. A month ago however, I ran into her on the street and she once again made an extremely rude comment. I chose not to engage, and she has since been sending me “anonymous” emails (but I’m 100% sure it’s her) just name calling and saying all kinds of messed up things. I know she’s baiting me into a fight because she’s so petty (and in the past, I’ve taken the bait because she’s really does know how to get under my skin, though now for the sake of our mutual friends I’m trying so hard to maintain my calm and be the bigger person). But the final straw really was when we were at a mutual friend’s mother’s FUNERAL, this girl “accidentally” spilled her plate of pasta all over my dress. It was so wildly inappropriate and disrespectful because it was DURING our other friends fathers speech (the husband of the deceased) I was not only deeply embarrassed but also soooo angry. I think I handled it well under the circumstances (did not make a scene, excused myself to the washroom and tried to clean it up). But I’ve just been so so angry about it since and I just don’t know what to do. A small petty part of me wants to take some kind of revenge, but I also think the best revenge to sheer insane pettiness is just indifference. Anyway. Needed to vent to people outside our friend group because it’s not fair to put others in the middle but FFS. she needs help!!!