So I know from experience that Reddit isn't the most understanding towards parents of young kids but I really just want a third party opinion because this situation is driving me crazy and my family are saying I need to get over it

I (F30's) live with my partner and our two kids, ages 7 and 3.

My older sister "Ava" (also F30's) and her husband recently purchased a house in the local area. It's a super nice place with a big yard and as you can probably guess from the title, a swimming pool.

Ava recently hosted a barbecue at her place. It wasn't a huge event, she invited me, our parents and our other siblings.

She mentioned letting the kids play in the pool so I only assumed my kids would get to be included

We are potty training although my youngest is still in diapers at the moment.

At the barbecue, I was getting my youngest ready for the pool by changing him into a swim diaper. Ava pulled me aside and told me she doesn't think it's "hygienic" for my youngest to play in the pool, since swim diapers don't hold pee and she asked that he doesn't swim in the pool with the other kids playing in it

I didn't think this was fair and told Ava that lots of people, adults and kids, pee in the pool and it would be no different at a public pool so what's the problem?

She was being really condescending and wouldn't listen to me at all and said that he can play in the pool when he's "toilet trained", and said it's not fair on the other kids.

At this point my son was crying because he wanted to swim in the pool and I told Ava she was being cold but it's her house and her pool so do what you want. Ava accused me of trying to guilt trip her and told me to just drop it.

I was getting upset myself at this point and i told our parents and other siblings about what Ava did. They told me it's not a big deal and that it's not worth arguing with her over and try not to let it bother me. I wasn't happy with this because this essentially means they're siding with her and downplaying how she treated me and my son.

I left the barbecue early with my family because we didn't feel welcome after that.

The next day Ava messaged me a whole paragraphs and said that she's "sorry" that I'm upset and that she wasn't trying to exclude my son for the sake of it. It was a super non-apology and I told her I don't want to hear it and that she's damaged her relationship with her nephew and shes not the one who had to deal with him being upset.

Ava snapped at me out of nowhere and said I'm being dramatic. I told her to grow up and said that I have a very valid reason to be mad, and she needs to stop acting like a teenager.

Ava showed these messages to everyone and everythings just a bit up in the air. I feel like I'm right here but the rest of my family doesn't seem to agree.