I think the 30 days is recommended to help insure that any ich/velvet that may have encysted on the aquarium can't re-infect the fish. However, if you move her to a disinfected aquarium, that concern should be eliminated. I'm not sure if you were treating her for something else using hypo though.
I'm not a tang person, but for most fish I think I'd prefer to stress them out a little bit with a move rather than try to continue to maintain the hypo for that long. Hypo is by far the least toxic approach, but it's still not ideal water conditions. You also could put her in the 5 gallon temporarily, disinfect her current aquarium and equipment, and then move her back to her home. You just need to disinfect everything (heater, filters, tank, etc). I usually use a combination of hot water filled to the top for 30 minutes and bleach.