Your dd thinks that shes protecting you, she doesn't want to cause problems, she sounds like a very mature and lovely little girl
You need to sit her down and say, " I'm going to speak to your dad and step mother about this because its wrong, and I need to protect you"
At 12 years old, alot of kids want to handle things themselves but this is an adult situation mum and you need to handle the pair of them yourself
You can assure dd everything will be fine and she needn't worry,
Show your daughter that you won't let anybody, not even her dad, disrespect or make her feel bad
When you to talk to your ex, just stick ti the points and be direct,
.Dd has been coming back from your house upset, shes refusing meals
.She told me that you and your wife have been making comments about her weight and teasing her, this stops NOW I'm not going to allow anybody to treat my daughter in this way,
.dd is still willing to spend time with you
There will be NO repercussions for dd confiding in me, she did the right thing to speak up about being bullied
.this is going to cause dd to have low self esteem
Pass this message on to your wife, I don't want to hear another word out of her about my child and she will be nothing but nice to dd from now on, ciao
If this bullying continues OP, your dd will look back and be sad that you didn't defend her,
Remember that shes only being silent because she doesn't want to be a burden, which is a side effect of your ex teasing her.
A child should never feel like they can't eat food in their own dads house, how effing dare that woman for saying that stuff
I'd be going around there face to face if this continues.
One thing is that adults do bully kids, teachers, parents, family, and the one thing that makes kids a target, if having no one to stand up for them
Children who have been in care , have uninvolved neglectful parents, or just parents who are passive, they will become targets for the predators and bullies