My 35F mom-group friend 37F, has a particular troubled kid... can I do anything??

Hello! So I'm part of a group of mom friends with kids ranging ages brand-new to 14. We're all living far away from our respective families, and we share a common language that our kids only speak at home. We've all bonded over wanting our kids to have a social/familial space in the minority language. Its become kindof like raising our kids as cousins. Unfortunately, theres one family, or more specifically one kid, who is throwing things way off.

Aaron (fake name) is seven, and he has a LOT of behavioral problems... no clear diagnosis, but he sees a therapist through school, and he also had to change schools last semester because he was getting into physical fights with other kids/hitting teachers. He once bit a teacher and she got several days of medical leave. He also hits his sister (eight) a lot and I've seen him spit on her or throw fairly substantial objects at her, like metal or glass water bottles. He essentially has no boundaries around either screens or sweet foods, and throws tantrums until he gets it.

To be honest, we all knew he having more trouble than the other kids his age with emotional regulation, but its really been the last few months that the rest of us have seen how violent the tantrums can be. He hasn't hit any of the other kids in the group, but the kids themselves have expressed that they no longer want to spend time with Aaron. Mine is the youngest, and blissfully unaware of any drama, but I'm fully on board with the other moms not forcing kids to socialize with someone whose behavior is risky or upsetting.

The problem is that we don't really know how to explain this to Aaron's mom "Stella". We've had conversations with her, and shes related advice about how to manage tantrums from their therapist, but she ends up giving in and handing over the iPad or the chocolate for a moments peace, or scolding their daughter when she 'provokes' a tantrum... even though shes usually just defending herself.

I feel really bad for Stella... she has her own mental health struggles, and her husband works long hours and isn't around much. Apart from this group she really doesn't have much of a support network. As bad as I think it is in the longterm, I can understand why after getting screamed at and pummeled by her kid for hours a day, she ends up letting him have that he wants. She loves the kid and kid be incredibly sensitive or defensive about whats going on with him. I feel bad for their daughter, because shes a very smart and engaging kid, but shes clearly starting to have some coping issues that are also a turn off to the other kids in the group. I feel bad for Aaron, because he can be a very sweet kid when hes not off balance.

The last straw was that Aaron just had his birthday party last week, and everyone ended up declining the invitation because their kids refuse to spend time with him. Is there anything to be done from a friend perspective? I want to preserve the relationship and support Stella and her kids, but I just dont know what to do for that to work.