Hi @Lonely11 I work with adults with disabilities - many of whom display what are called "challenging behaviours" (sometimes aggression & violence).
I have worked with children, although not recently.
What you describe does sound like a delicate & difficult situation for you, not just the child to be in.
You did the best you could, & communicated how the child felt (& the possible school difficulties) to her mother.
Yet you seemed to have been not believed, or met with denial (by her mother).
Yes I have been faced with some similar situations - yet I have never been given anywhere near adequate support, for me to deal with those situation.
My clients frequently refuse to participate in the activity that they are supposedly doing (that day) - my management often will not acknowlege any "non-compliance".
Instead, they often expect me to magically "make the client do it" (without force of course) - Making anyone do something (when they do not want to), is not really possible, & is not the purpose of the activity (in any case).
The resources that @Former-Member suggested, may be helpful.
For those options to work or provide support, your young person needs to be interested & willing to try it (first).
Which is a challenge in itself.
I'm sorry I could not be of more specific help.
I'm thinking about it, racking my brain, as the saying goes....
Adge