Were you an only child, OP?
Some of us view this as normal because we were picked on by siblings, cousins or we picked on them and it was just a rite of passage! It taught us to stand up for ourselves, set boundaries, have a laugh, distinguish certain motives from others etc.
This scenario (appreciate I wasn't there) sounds like the kids were teasing and probably being mean but in a normal 6 year old way and not a horribly, bullying way.
I know it can be upsetting to watch your child look upset but, sometimes, they use these mannerisms as a way to signal to other children that they're not happy with their comments or behaviour which is very healthy.
I was very overprotective of my DC but I learned my DC teased others, too, so quickly understood that this was their way of communicating at this age.
There are a lot of phrases which are used in the wrong context and I think it's made people hyper sensitive to labels and being accused of motivations and intent that don't apply.
Not saying it doesn't apply, but hard to tell based on what has been said and just trying to help you understand some of the responses.
Glad she's found some new playmates!