Poor child.
Sad that her parents have split up, but worse to have new partners within five months, giving the children no time to adjust to a huge change in their lives.
School is a constant in their lives and you will be too; don't talk too much about mummy and daddy unless she raises the subject; if she does listen hard but avoid commenting too much. Try to keep everything as normal and undemanding and unchanged as possible and ignore the fact she isn't being very nice; she is pushing you to see if you will change, and venting her disquiet and anxiety on you. She is uneasy about leaving home and returning because she doesn't know what she will find whereas school is predictable.
Don't criticise her parents in any way and remain neutral about the new partners.
The effect of divorce on children is covered up and so many parents claim they aren't affected at all, because they don't want their exciting new lives spoilt, but things do settle down eventually.