I'm curious what the deciding factor was in bringing her back to you? The farm sounded ideal.
Start putting notes up at all the Vet Offices in the area. We have a county-run ASPCA Shelter that has a 97% success rate. Look for a similar shelter, you already know she needs a one dog home. Any idea how she is around cats?
We had two dogs, a huge 100 # Collie, and a smaller Scottie/Corgi mix both intact males ( Max & Sam ) who fought whenever they had the chance. Even seeing each other resulted in them both trying to go through the glass. We managed this for a good five years of keeping them out of sight from each other. We would separate them by floors of the house and that worked pretty well. It would break down when visitors came who did not understand the reason behind the gated stairway. I would suggest having a barrier separating the two dogs until you find a home Lyla. I know what you are trying to manage and it is frustrating as hell. I wish you and Lyla luck.