
For what it is worth, here's my personal experience of two bitches that did not get along.
Elsa the Golden is 3 years older than Ripley the Malinois, so hence lived here first. When Ripley was around 2 years old, Elsa started trying to put her in her place. At first little things, like if you were talking to Ripley, Elsa would push in front and demand attention. Then bigger things, like actual attacks -but it was always in certain circumstances. I.e. say I did a down stay with both (or all the dogs), once the release word was given so they dogs could move Elsa would jump at Ripley and bite. Once during a walk I grabbed Ripley's collar to restrain her, and at once Elsa jumped on her neck -and managed to bite ME; as my hand was on the neck. It went on like this, and each time it became more and more serious.
It was suggested to me by a behaviourist that one of the bitches needed to be shown clearly that she ranked higher than the other, and that I needed to chose one. I chose Ripley simply because she is the more sensible one in many ways, and although younger, the stronger. So we started to feed Ripley before Elsa (this is one situation where order of feeding can make a difference- but between the DOGS themselves), Ripley would be taken for walks without Elsa, etc. It worked. Soon Elsa stopped pushing in, she'd hang back and wait her turn for attention etc. We've kept at it ever since, about 3 years now, and they are absolutely fine. However we do still have to be careful as to not blur the lines between them. As Ripley is higher ranking than Elsa, it is fine to for instance take Ripley for a walk without Elsa. We cannot do the opposite. If Elsa has had extra attention without Ripley, arrives home again, she attacks Ripley immediately. Just before Christmas Elsa had surgery and we kept her away from the other dogs whilst she had stitches in (to stop the others from licking her stitches) and she was with us most of the time but the other dogs were in the kitchen. That was a mistake. When she and Ripley was mixed together again after a couple of weeks, Elsa believed she was now more important as she had had the individual attention, she jumped at Ripley and the result was us spending Christmas Day at the vets waiting for Ripley to be stitched up in 3 places.
When Ripley has been separated for a while, such as to have pups, or just having been to a show, for a walk or to training, and then is allowed in to the other dogs again, she will walk up to Elsa and stand over her, hackles raised, showing she is in charge, but she will never hurt Elsa (and under these circumstances Elsa gives in and shows her submission) -this is what I mean about Ripley being more sensible. Under the same circumstances Elsa will instead attack, with serious intent.
So we've made it work and when it fails and they do end up fighting it has always been our fault.
I had a similar situation years ago with two dogs, but that was easier and quicker to solve -it just took one day of making it clear which was the higher ranking dog (by giving him lots of attention and ignoring the other) then they never fought again for as long as they lived and in fact were best friends.
Marianne