Considering you'd had the dominant girl long enough to know she was aggressive (e.g. the fight she instigated with the Lab when she was only seven months old), it was a poor decision to bring another dog, regardless of sex, into the home.
Now you've got a dog-aggressive bitch with, what sounds to me, like displaced aggression
(see link below and quote highlighted for reference), and a submissive bitch who is likely becoming increasingly reactive and could develop fear-based aggression, in which case, may discontinue her time in the ring if her temperament doesn't remain stable. Of course, that may already be over with considering the gashes, staples and eventual scars... Dealing With Aggression
"One common denominator in all of the reasons for biting, is displacement. Humans being bitten are very often the result of displacement behavior by the dog, rather than true aggression directed towards the human. Displacement has a great deal to do with the nerve structure and clear headedness of the dog. Highly excitable (nervy) dogs are very likely to bite in displacement."
So, if you decide not to crate and rotate, your only other option would be to remove one of them from the household. Considering the older bitches' bite history, I doubt any rescue would be willing to take her. And it's likely she will have to be put to sleep.
If you choose to rehome the show bitch, please be sure to have her spayed
beforehand and placed in a home without other pets or with dogs whom she shows no fear reactivity toward. Hopefully, she will forget all about it and start anew, as dogs seem to have that gift.
And if you do rehome the show bitch and keep the older female, I hope that you'll consider not bringing another dog into your home for the remainder of the life of the older bitch. Just give the older gal a great life and maybe pick up your show career with a new pup down the road a bit?
It's a tough situation, and I wish you the best of luck. Keep us posted.