If you can get a bit of her milk, and rub it on the babies, it might help.

Occasionally, momcats are like that.

Have you asked your vet about this?

I know a few people on this board have bottle fed kittens - jenluckenbach, reachoutrescue, etc. It sounds like you know what you are doing.

Is there a friend who can spell you off every so often so you can sleep?

HUGS