Crazy thought: what if we...normalized forgiveness when someone makes a genuinely good apology to you? Like actually forgave even if that person doesn't know? You know, to like, stop letting hate grow in ya? I know, I know, sounds wild but just a suggestion.
If you have the ability to leave the room, end the conversation or avoid the gossip go ahead and do that.
It's not worth ruining your vibe, spending your energy and damaging your reputation to trash talk others or getting involved in situations that don't bring you any benefit.
Don't forget to drink water and mind your business. The drama is not worth your peace. Let it go.