Even if you try to deny it.
a 5 years old child does not understand that the mommy cat will just carry her kittens that way.
For a 5 years old child this behaviour is plain and simply biting - as a cat would do with it's prey- period.
Othewise your daughter would not have tried to get the kitten out of her mouth by pulling while yelling "Houdini your hurting the kitty" but would have asked you for advise instead.
Bring the kitten to a vet immediately - if no vet has open bring it to a 24/7 ER vet clinic immediately.
It requires adequate treatment for the huge wound (compared to it's body size) - even if it was not visibly bleeding, and also antibiotics.
The cat's saliva contains natural germs which could trigger severe infections in bite marks.
If you can't afford it, bring it there anyways - even if you have to abandon this kitten.
Her mother will kill it most likely as she would do with injured kittens in the wild.
Simply because she things the kitten has no chance to survive and killing the injured one allow her to focus on the healthy kittens.
And please never ever let your daughter unattended with the kittens. Bring litter box, food and water to the kitten room and leave the mother cat and her kittens locked in the room when you are not able to observe your daughter.
Note beside:
The more you ask not to be judged, the more you tell that you knew who had to know better and who is responsible for what happened.
Therefore.
Show at least now responsibility and bring the kitten to the vet immediately.
If you abandon the kitten, it has at least a chance to survive - otherwise it would be dead within few days.
Imagine something equal would happen to your child in the day care and the care giver decides not to bring your child to the hospital because she has no insurance and can not afford it.
Even the head line ... "... caused by mother cat ..."
The wound was caused by your daughter who was trying to pull the kitten out of mommy cat's mouth - so do not blame the mother cat for what happened.
Sorry, there is only one person her who is to blame for what happened - and it's neither the cat, nor the kitten, nor your daughter.
And the mother cat pretty sure was trying to move her kittens out of your daughter's range.