What to do with 2nd mother

Ok folks, not sure if this is a vet question or not. We just had 2 females a week ago give birth to litters, unplanned, 1 day or so apart. Our Penny's litter was 5 healthy normal puppies and 1 stillborn. Snow had 3 puppies one was still born we assume as she gave us no signs she was in labor. 2 were born alive and unfortunately we didn't know Snow wasn't producing enough milk until I went to vet 4 days later as Snow was not acting right. All 3 puppies were very small and the 2 living were always cold. Her third puppy died a few hours back from the vet and we think it was just too cold even though we did feed it with puppy formula and a hot water bottle. Well her 2nd puppy which we kept alive with hot water bottle and feedings just died within the last couple hours after we went to bed. Woke up to Snow crying at our door with the puppy in her mouth and it was already cold and stiff, must have died very shortly after we went to bed. So here's our dilemna. Snow wants to sit with Penny's puppies. Penny isn't fighting her or even growling at her because they've been around each other's litters. At first they both growled at each other when they got within like 5 feet. Do we allow Snow to sit with Penny's litter? Do we split the litter and just keep rotating puppies to make sure they are fed by Penny. All Penny's puppies have grown considerably and are fat happy little puppies. Or should we just put Snow outside and let her whine and probably be very depressed. Snow already hasn't been eating much for days so I'm concerned that she may not eat at all and we risk losing her too. I just don't know what to do.

Hello!  - there are days in this job that I feel I say 'I don't know' a lot, and this is one of them.  There will doubtless be many opinions about this, but it is hard to give the right answer because the right answer depends on the individual pup and the Mums.  There are risks and potential gains in either direction and given a crystal ball, it would be easy.  Most owners in this position will follow their instinct, although your vet might point you to specialists for better advice.  If you do decide to let the Mums share, obviously supervise them as much as possible to be as safe as you feasibly can in the situation.  However, there are no guarantees in either direction.  All the best and please let us know how things went.