I seldom post, as I either don’t feel strongly about the nature of the post, or I don’t think I have anything useful to add to what’s already been said.
My take on this is:
Short Version
Never wrestle with a pig. You both get dirty and the pig likes it.
Long Version
I do think OP has been treated appallingly by this woman, and her behaviour is so unusual - in an adult at least - that it would put most of us on the back foot in terms of how to respond.
What concerns me a little is the number of posters who are suggesting a mental illness or clinical behavioural issue. I guess this is because they are so aghast and perplexed by this individual’s behaviour.
I’m not a medic, however I have a lot of experience as a patient! I’ve received medical help for severe depression for around 30 years. It has, on occasion, altered my thought processes so radically that with hindsight I’ve thought, “God, how could I have thought like that?”, or “God, what was I doing?”.
Happily, I’ve learned how to mange the depression with medication, CBT and so on, and have been pootling along nicely for decades. However at the beginning, when I was suicidal, I was an in-patient and then a day-patient in a psychiatric hospital and was signed off work for a year.
During that year, I met lots of fellow patients and, apart from their respective mental illnesses which ranged from severe and uncontrolled delusional psychotic episodes, to more run of the mill stuff(!) like depression, they didn’t go around systematically being unkind or horrid. Many were intelligent, witty and creative. Some I liked a lot, a few I didn’t, most I got on with. They were just ordinary people. I made some good, lifelong friends there.
However, there were a few - just a very few - people that everyone learned to be wary of. They were ostensibly okay, but underneath they were rotten / nasty, take your pick of words. I’m not talking sociopathy / narcissism or whatever - we could spot those! I mean just ordinary, bog standard horribleness. They were never happy unless they were in the middle of some upset or other. Not all of these individuals were patients! The one I remember who was a nurse was an utter pain and caused ructions amongst patients and staff alike. However it was interesting to observe that of those who were patients, they were still rotten / nasty / horrible once their clinical symptoms had been controlled. This part of their personality was completely separate from their mental illness. As Bob, a rough-diamond patient said of one, “He used to be a mad cunt, now he’s just a cunt.”
The point I’m trying to make is, please do not use mental illness to scapegoat this person’s behaviour. Even if she does have a psychiatric disorder (I’ve not read anything that suggests this), this does give her a Get Out Of Jail Free card for her behaviour and shenanigans.
I’ve come across a few individuals like this in my life since the stay in hospital. Not many, thank God, but I’ve learned to give them the Big Swerve. Call them rotten / nasty whatever... they’re bad news and are unredeemable, so don’t waste time thinking oh, I’ll just try to build bridges la la la. Doesn’t work. Just uses energy, causes anxiety and hurt and actually encourages them (see pig saying in Short Version above).
It’s up to the OP how she manages this, but I think I’d keep ignoring this person, and I’d make a point of avoiding any engagement with her at all in the future, whether directly or via friends. At the very least, I think the OP’s priority should be protecting her own mental and emotional well-being. I’m not suggesting that she jettisons all the other ladies in the friendship group, but maybe start to develop other, separate acquaintances and interests.
As for softzilla, she’ll eventually move on once all the juice has been sucked out of this scenario.