Two years old is getting to about the standard life-span for a pet rat. I’ve just had two die in quick succession at just over and just under 2 years old.
All of my boys are looking a bit shaggy now. Especially those who have rex genes (curly coat/whiskers). They’re prone to patchy fur anyway, but like any elderly animal the fur thins and they start looking a bit ragged.
If she’s otherwise healthy and squeaking along happily then it’s no big deal. You may want to keep an eye on her weight though. Rathbone started looking a bit raggedy, but then his weight suddenly plummeted and he deteriorated quickly, dying in his sleep overnight after I’d had him in the isolation cage and had been hand-feeding him for a couple of days.