[souffle]

They are quite old hammies now and weight loss is common in older hamsters.
Unfortunately extra protein at this age doesn't really help as they don't absorb it that well due to their organs weakening with age.
If your little one is still happy and doing her normal things it is likely just age related. You have done your best and got her vet care so I think you should enjoy her twilight times. You never really know how they will fare when they get older so it's really a case of one day at a time.