OP can I just say I hear you loud and clear.
To give you an example a parent at my child's school actively moaned about some other parents putting them down as benefit scroungers and when she mentioned a bitchy throw away comment like I challenged her and now I get subtly bullying now in return. All the time.
She has quite a close set of friends so they get together and laugh at her putdowns.
So I am given the silent treatment.
It is quite awful bumping into them as sometimes she will be patronising and then I get silence and glares.
It is really difficult and just awful but it seems to the school they present themselves as caring parents if you see what I mean. So teachers all think this person is great as she self promotes.
I was working and now are a sahm but want to get back to work.
With this kind of ring leader - If I suggest something productive then she never agrees. I don't want it out myself but she has a gatekeeper fundraising role.
I offer to help with stuff and am only informed at the last minute.
I think trying to speak to other parents (who are NOT part of her clique) just to chat would be good and you don't have to mention the bully.
You can always ask the school for feedback on your child and they will give it but if you child had issues I would have thought you would have been informed.
Make other friends if you can but you are working so don't stress.
Also consider having a quiet word to the school about your child's behaviour and bully.
I think,like others said, saying something like "are you sure you meant to say that about a child it sounds rude?" Is a good strategy.
Good luck