Is my daughter being abused when we aren't looking?

If there are marks and you notice a change in behavior, you should investigate this and if it were me, I would not leave her alone with these people until your investigation is concluded. Is it possible to find a different babysitter? Your roommate may not admit or notice this so for something like this, it does not hurt to error on the side of caution. The law says leaving marks constitutes abuse.

To be honest this pissed me off a little. Please have a heart to heart with your roommate and then get your child out of the situation. I understand that you may be trying to protect your relationship with her, but your daughter must come first. Even if your roommate speaks with her children they may find new ways to torment your child. Sorry to say it but it is true. Bad things can come from any person at any age. Please ask your roommate to leave and do not wait for video proof

Confront the roommate ASAP, let her know you are concerned about the marks on your daughter and you'd like to know where they came from. It's not acceptable for someone caring for children to let other kids abuse the younger ones- that's neglect.

Yes it does sound like child abuse. I'd question your roommate about the bruises after I notify the police.

That's horrible!

Maybe you should talk to your roommate, or maybe even move.

Your daughter's safety should be the most important thing, and even if you don't know how she is getting injured, she is.

Maybe next time you should stay with them while they play, or be a secret agent and set up a video camera.

Trust your instinct on this one. If you suspect something is wrong, don't allow your daughter to be left in the care of these people again.

omg i hate that. i hate abuse period. i almost cried reading this. don't let her stay there anymore please. have her stay somewhere else for a month or so and if the marks are still appearing i would take her to the doctors or something.

get her away from them! and possibly call the police. thats horrible and they should be punished.

are the wounds on her butt or elsewher?

if elsewhere I would seek police help.