You are way too over invested in this, and your last comment was vile.
At eleven friendships are fluid. They come and go, and even if they were friends when they were seven it’s highly unlikely they will still be friends by the time they’re twelve. This is just how it is.
As for you getting involved and speaking to the parents and telling your DD what to write on snapchat, you are probably making things worse for her not better. I would have been mortified if my mum had got involved in my friendships at that age, and in truth you’re setting her up for more bullying (if it actually is bullying, I’m not sure it is) because the other girls will be able to say that “x can’t stand up for herself, she needs mummy to do it for her.”
The one positive about online bullying or even bad feeling is that all social media has a block button. DD doesn’t actually have to see these comments, she can just block them.
But it seems that you are desperate to control her and her friendships to such a degree that you’re even telling her what to write.
And your DD needs to grow a thicker skin. yes, kids can be cruel. I have no idea what they’ve said about your disability but this is also one DD is going to have to learn to ignore. Most of these kinds of comments are made out of ignorance, and most kids don’t even know what it is they’re saying.
Clearly your DD does want to be friends with these girls, so you’re just going to have to leave them through it. There will be angst, there will be hurt feelings, friendships will be won and lost. This is life.
Oh and, I do have disabilities, before I’m accused of not so not knowing what I’m talking about.