I am sorry to hear about Beulah and Rosie not getting along. I am a veterinarian and will do my best to help.
This is a sad, but not uncommon situation that we see. Two female dogs, living together, but when the younger one becomes emtionally and socially mature, around 2 to 3 years of age, if she decides she wants to be "top dog" she starts to challenge the older female. Sometimes the older female gives way and accepts the younger as the new boss. If she does not give up her status to the younger dog, and the younger dog does not accept her as the higher status member of the "pack", then they fight over anything that dogs consider marks of ownership or status: sleeping places, who goes through a door first, access to " resources" (which can be food, toys, a used Kleenex, or even access to you and other human members of the pack).
This is a very difficult situation, because we humans can't make them get along. They will alway be challenging each other, unless one agrees to be submissive, and unfortunately that rarely happens.
I work with a breeder and trainer and since I never have found any hope for this situation of two spayed females not getting along and she also said that female/female aggression is the one behavior problem she has no answer for.
If I had two females in this situation, I would either find a home for one of them, or would start to live with them separated. The one thing I do that sometimes helps won't work with Pugs: I put a head collar like a Gentle Leader or Promise collar on them, with a long light lead attached, at all times, so I can pull them apart the minute something starts, but these collars do not fit dogs with short faces.
This is so typical of this problem: used to be great buddies, and then suddenly when the younger female hits 2 or 3 years, they start to fight. I wish I had a quick and sure fire answer for you, but I have worked with dozens of dog owners in this situation, and it always ended with one dog seriously hurt, or rehomed. I have tried behavior modification, drug therapy (usually just makes it worse), and sending them to veterinarians who specialize in behavior and the outcome has always been the same.
Sorry to be the messenger of bad news, but I have to be honest. Let me know what else I can help with or answer. Rebecca