Other mum disciplining daughter in front of me

I'd tell her to give her the opportunity to alter the behaviour. Arrange to meet up once more and if it continues don't meet again outside of swimming.

That's presuming this is the first time she's been like this with your child and you feel like the friendship is worth saving.

Sounds like her kid was being a brat, if she didn’t want people near her the mom should pick up on that and give her a break from the public space. How would they have reacted if OTHER children went near her when she wanted space?
I’d rip the mom’s head off for talking to my kiddo like that. Real ones don’t “tell it like it is” when it’s already been dealt with.

The only exception for anyone to address another persons kid at all is when one child is trying to hurt another.

It’s up to you how you handle that.

Personally I would tell her flat out I’m not interested in her company if she ask to catch up, say she gets rubbed the wrong way from you being honest it’s not your responsibility to comfort her.

I’m a very hands on mom myself and I remove my child from the fun when she’s in a bad mood or getting tantrumy especially in a shared space.

I'm a bit torn here as my son has been in situations where children are pushing personal space and boundaries. He has a best friend and they go to school together as well as do play dates and I can see it overwhelm my son sometimes. We reinforce saying a firm 'no' but it's one area my son isn't that strong in. Sometimes we do have to step in and just call the other little boys name to remind him what is safe and ok around our son. His parents are normally there and will also step in but they are much more gentle in their approach. Boundaries and personal space for us is a big thing and I do encourage eventually swinging his arms out or pushing away if someone repeatedly enters his space. Personally, if it were the other way and and she was having to tell my son, I would start stepping in more. I would prob remove my son from the play situation for a minute to give them both a break or I would explain about space to both of them.

There have been other occasions in classes where another kid was putting his feet on my son and telling him to act like a dog. My husband called the child's name and told him to stop. His parents weren't even there watching him but it wasn't ok and he was a slightly older child. I usually follow the other parents lead, if they are saying something, I need to reinforce too but choose my way to tell my child before another parent chooses to step in. If that means leaving early so be it.

I completely agree with Natalie.
I’d either talk to her & let her know that she’s been harsh, or I would give back and talk to her little one the same one just to see your friends reaction (controversial I know!)
Failing that it doesn’t sound like it’s a friendship worth saving x

I would 100% tell her that it’s not her job to correct my child, she honestly would have gotten cussed smooth tf out and I would have left right then and there to prevent an altercation. Don’t disrespect my kid, and don’t let your kid disrespect my kid or we’re going to have a problem.