My ex has meet a new girlfriend and has bin taking my 7 year old girl there to sleep, but has bin putting her with her son who is 9, is this OK because I'm not happy, she doesn't even really no him

If the situation makes you "unhappy" you have every right to go back to Court and ask that the Court order that your child has her OWN bed when she visits and possibly her OWN room.

You might also be able to stop the visits with the girlfriend and your child.

If this happens only occasionally I don't see where a court will take action.

You should explain to your daughter about inappropriate behavior and ask that your ex do the same for the girlfriend's son.