AIBU to challenge a comment about DD on social media

[Zeusthemoose]

This is just a quick question asking for advice please.
My DD is 11 - someone has told her a girl she knows from a different school has been saying really unkind things about her on a group WhatsApp group. It's really knocked her confidence. So I'm thinking of contacting this girls Mum. Is this the right thing to do or at this age do you stand back a bit and just teach kids to bat this kind of away and not waste energy on it? There's no background between the girls or reason I'm aware of why she's doing this.

Nope. Group chat isn't the same as social media. Nor are email groups, for example. It's lazy conflation.

No, it’s your opinion, which I disagree with. As does Whatsapp, incidentally, which is probably why its minimum age limit is now 16. Eleven is too young for group chats.