Are you wanting to register her as a form of proof of ownership? If so, I wouldn't mess with it, even IF she is eligible. It's likely her appearance is the same as hundreds of other sheep, so how, if you were challenged for ownership, would you KNOW which one was yours?
Since it is one sheep, I would talk to a vet about microchipping her. That is concrete proof of ownership, and you cannot be deceived by appearances. Of course, you will need a scanner, but those are widely available. In horses, the chip goes in the nuchal ligament so it cannot migrate, and it is a known area to scan.
That and LOTS of photos from every imaginable angle, notate any sworls in her hair on her face/legs, etc.
Ear tags are great, too, but they can be lost, and they can be replicated on another animal with her appearance.