DD says that her friend (9) makes herself sick to avoid school

[Melpomene]

Conversation with my dd this morning on the way to school:

DD: I wish I didn't have to go to school. X makes herself sick when she doesn't want to go to school.
Me: How do you mean, she makes herself sick?
DD: Like this (mimes sticking fingers in her throat and retching)

DD and X are both 9 and are in the same class.

Obviously I can't be sure whether X has actually made herself vomit or just pretended to her friends (or even whether my dd is making it up.) I don't know whether or not she has had days off school. But the worst case scenario is that X is making herself vomit, harming her health and spreading this idea amongst other girls at an impressionable age. I know X's mum a little, and have her mobile number, but don't see her regularly and when I do see her it's usually just for a few seconds at drop off time with lots of other people about.

So, should I phone X's mum to tell her what my dd said about X making herself sick? Or would that be too intrusive? Would you want to know if it was your dd? What would you do?

I honestly think if this was my DD I'd want to be told so if she had been missing a lot of school recently I could ask her if this was what was going on and explain why its such a bad thing to do and also get to the bottom of why she didn't want to attend school.

I think it would be tricky to bring up with anyone however but just mention that it had you worried and you thought that for safety's sake it would be a good idea to mention it to her Mum.