They are giving out their phone number to people they met on roblox.
The child is institutionalised, their parent cannot control their behavior meaningfully and the adults at the institution are pretty negligent and she doesn’t trust them.
I have messaged like my whole family and some friends for advice but nobody is getting back to me.
You can talk to her and be very clear about the dangers and the type of information she should not share on the internet. If you search for parenting resources on online safety you will find many resources that can help you prepare such a conversation.
And depending on the type of relationship you have with her, you can also tell her that she can always come to you if she finds herself in an uncomfortable situation online. It’s important that she doesn’t regret admitting this to you and feels safe to ask for guidance.
You can also sporadically ask her what she’s doing online to check if she’s following your advice.