I have been one of the onlookers as my friendship group imploded resulting in one good friend who now no longer speaks to my other friends.
The problem is that both sides believe the other acted in a reprehensible manner.
I can listen to both and empathise a little but I try not to get too involved tbh. I wasn't there when the incidents happened which led up to the split and ill feeling. I can sort of understand where both sides are coming from and what they feel and what they believe happened. However for me it is impossible to take sides as it doesn't really involve me at all, I wasn't there and it also seems a bit six of one and half a dozen of the other.
I get why you feel hurt and abandoned, particularly when it seems that this woman is fighting dirty. It may be that your other friends are just trying to be diplomatic and not stick their nose in where it might not be wanted by making judgements or accusations.
However I am sure your friends will have also clocked that this person is speaking badly of you and is quite possibly lying/fantasising/deluded as well.
Personally, if I hear someone speaking badly of someone else it always makes me a bit wary and suspicious of them. If they do this to someone else I always wonder what they might say about me. And it makes me respect them less as a person tbh.
So my advice to you is to maintain the moral high ground. Don't indulge in gossip or slagging off the other woman. Let her dig her own grave with your mutual friends.
And she will, you mark my words...
Be the bigger person here and keep your chin up love.
It will all blow over soon enough 