I've spent all evening reading most of the threads on here about aggression.  One of my girls has just had a litter and the other (more dominant) came into season just after the pups were born.  I kept them apart until the mum stopped feeding her pups and the other's season finished, at which time they both seemed accepting of one another.  Pups have left for their new homes and I've had a couple of weeks thinking harmony has been restored and all is well with the world but for the past couple of days the more dominant girl has been getting very growly and stroppy.  She has always been higher in the pack than my other girl.  I think I read somewhere about a dog's status being raised if she has a litter.  Does anyone think there is any truth in that?
She is perfectly fine with us humans, just looks like she is going to tear my girl's head off any minute!  Is this just a temporary hormonal imbalance, or am I doomed to a life of closed doors?
So, if any of you brilliant folk out there have experienced anything similar, or have any ideas or suggestions on how to defuse this situation I would very much appreciate hearing from you.
Thanks!

I never split my girls up from the other dogs other than the others not having access to the litter for the first two to three weeks.  Mum has to go out where the others are in the kitchen.

I certainly do find that having a litter,and the special attention they get does rather raise their opinions of themselves adn a bit of firmness is needed to stop them getting above themselves.  If this is normally a lower ranking bitch then the ones used to her being lower wil feeel the need to assert themselves, and this is often the tieme  when a shift in pack  dynamics occurs.

I have found thaqt watching and jumping on any situations to difuse conflict is needed.

Any splitting up makes things worse, as when introduced again they feel the need to sort out what's what.

I kept them separate for the first couple of weeks, as mum was protective of her pups and this seemed to be the best thing to do.  It also seems to be what most breeders do.  When I reintroduced them it was without the pups and they were happy to play in the garden together.  From what you have said do you think there is a good chance they will settle down together?  Everything I've read implies once girls fall out that is it!

Could the second bitch be developing a phantom pregnancy which is making her particularly moody?

Phantom pregnancy came to my mind too. She could be thinking she is about to, or even given birth to, a litter a pups and is guarding them, or her nesting site.

I never split my girls up from the other dogs other than the others not having access to the litter for the first two to three weeks.  Mum has to go out where the others are in the kitchen.

That doesn't work for all bitches. I have one that cannot be anywhere near the other bitches as soon as she has been mated -it would result in a fullblown fight which of course could result in a lost litter. She can go back with them once the pups are a few weeks old, not before then. Was the same for both litters.

Vet check for false pregnancy as sounds to me like hormonal imbalance is probably at the bottom of it. Even more so as there were pups in the house, in fact I would treat with galastop regardless to completely rule it out. False preganancy can have so many differing ranging symptoms, had 1 client who's dog was fab until season then would guard the male owner and was terrible around other dogs, that was there previously but highlighted with the hormones. Vet they saw was a plank, who didn't check dog over properly until client prompted him, gave them galastop told them to lead check the dog continually for aggression. Eventually all subsided with treatment and no lead checks needed. And owners are now married!!  

I have generally found that the more dogs are split up the harder it is to et them back together, though obviousy there are exceptions.

The way my house is set up there would be no way for the bitch to access the garden without going through the kitchen, which leads from living room, to which the others access is restricted while pups are first born.

It's another reason I can't own males or dogs that can't be mixed.

Such things like available accomodation all contribute to the way we manage our dogs.

This is why it worries me with various suggestions of what constitute good breeding re facilities as one size does not fit all.  So much will depend on the individual dogs, breeds, numbers kept, etc.

Thanks for all the advice and thoughts, they are much appreciated.  The dust seems to have settled a bit, although not 100 per cent fine.  I'm planning a few nice days out with the two of them, which I hope will mean they will reconnect as friends.  It is quite easy for me to keep them apart from one another in the house, so it is tempting to do that 'just in case' but think it will be better for everyone if they can bury the hatchet and move on.