I have a dog whos is acting strange with her pups. If I only let her with them to feed, how often does she need to feed them? Is this the best thing to do?

Hi,

I have a female dane who just whelped 2 days ago and somethings just don't seem right. She licks them too frequently, aggressively and vigorously and their stomachs are raw and I know they need this to poo and pee, but I have whelped a number of litters and never had a mother do this. She steps on them heavy footed she laid on one and did not move even though the pup was screaming. Usually after a female steps on one she starts tip toeing around, this one does not. Last night I heard her growl, I went to the box and there was a pup sucking on a nipple not completely formed and then she snapped at it twice. I'm afraid to leave her alone with the pups. She's very attentive and feeds them well but something is wrong with some of her behaviors.

If I only let her with them to feed, how often does she need to feed them and do you think this is the best thing to do?

Thank you in advance,
Pat