Maggie (spayed) and Lucy (intact) have been inseparable since they met. Lucy is alpha and Maggie is happy to be her buddy.
We brought home a female (intact) foster who came into heat within 2 days of Lucy once, and we had a few skirmishes, instigated by the foster...and quickly put down by Lucy who referees any issues within her domain.
Then we brought home Brenna (spayed adult rescue) who is a totally different cup of tea. VERY dominant/take no prisoners type personality. We tried for over three years to integrate her into the Maggie/Lucy pack. It worked for a while, then Brenna jumped Maggie with no warning. We broke it up, and put them both on notice, and kept a close watch on them if they were near each other.
Nothing happened for a while, so we thought that was it. Suddenly, Brenna jumped Maggie again, (again, without any grumbles or discernible change in posture, which would give warning) and this time she would not let go. This time, Maggie fought back as best she could, with Brenna having a death grip on her ear, cheek, and neck. Maggie chomped Brenna's foreleg in several places, putting big puncture wounds there. This seemed to be the turning point...at which they both declared war on the other.
After taking them separately to the vet, to get patched up, we kept them separated in the house, by giving Brenna our front room, with gates across the doorways. Brenna was still "part of the family" and could greet people as they came in the front door, but couldn't physically bother Maggie.
That worked, until one day when hubby had put Brenna up in our bedroom with the door closed. Maggie went upstairs, and upon finding the door to our room shut, she laid down against it. Unfortunately, the door popped open under her weight, and Brenna launched at her. Again, Brenna locked her jaws on the side of Maggie's neck, and just kept shaking and shaking her. I literally broke the wand of the Dyson over Brenna's head, to make her let go. That's all I could find to grab, so that's what I used. The jaws of life could not loosen her grip, but seeing "mom" swing the Dyson at her finally made her come to her senses and back off. I hated to do it, but Maggie has an arthritic neck and spine, and seeing Brenna shaking Mags like that just made me see red. After this, I was afraid to have Brenna on the same floor with the other two, for fear she'd hop the gate and go after one of them again.
Brenna is now the queen of our basement garage, and is hubby's buddy when he's working on cars (which he does in all of his free time). She is happy to rule the roost down there. Maggie and Lucy are much happier as a pair again, living upstairs. We just coordinate their inside/outside time, so that we never let Brenna out, if the other two are already in the yard. The one time that we accidentally let Brenna out, when the other two were out there, we were able to get Maggie in before they tangled much. Lucy totally held her own, and gave better than she got, because Brenna had several cuts on her neck, ears, and cheeks, where I didn't find more than a slight bruising on Lucy. I had been quite worried about that, because of Lucy's heart defect, but Lucy is quite quick and agile, in spite of her bad heart.
So, we have two females who adore each other, and one who doesn't like other dogs, but is quite happy having her own space, as long as she gets plenty of attention from her people.
