Stealing things at school

[user1474652148]

I am cross. I know this is a form of bullying, and having just posted to someone else to suggest calling the school...I am wondering whether I should do the same.
My dd (nearly 12) is good friends with all the girls in her year, and is very laid back, my dd and another girl have recently become very good friends, and it has sparked jealously with the other girls who used to be good friends with said girl (queen bee I suspect)
Today one of them (and I know which one) stole my daughter's favourite teddy key ring, and will not give it back to my dd. I am not sure what to do, the same girl keeps putting my dd down in a subtle way for the last few weeks - but my dd has just ignored her, but now it is becoming more difficult to ignore now this has happened.. Any suggestions? Shall I just replace th keyring, pretend it didn't happen and move on...or do I nip it in the bud?

I do know the mother quite well, so could speak to her, but my dd would be mortified she really does not want a fuss made...what would you do?

[MoominKitten]

Maybe reading this would help