Message his mum?

[Janegoldberg]

Checking dds social media see some boy has put up that my dd is a fat slag who cheats! Aibu to show this to his mum on fb and ask if is removed?
i don’t know her but can find her on there

Take a screenshot so you have evidence.

Are they at school together? Or do you know which school he attends? If so, inform the school.

How old?

Absolutely do not get involved with your child's friend's parents. I hope she's aware that you're checking her social media. Talk to her about it for sure, work out who this little scrote is to her and why he's talking about her that way.

Absolutely do not embarrass her by figuring out his mother on social media. If you knew her it might be different.

At diff schools she goes to school with his brother
his mother is the school safeguarding lead

She’s begged me not to as she says it will affect her
im so so angry
she’s had a girl start a lie about her and then this boy carry it on! So called friends too! Disgusting

yes inform the school

Don't do it now. Sleep on it. Spend time thinking about the best way to say it.