Do doctors know why it dropped so much in one year? Is she hydrating?

I hope she can get a Cystatin C version of the eGFR which may be better. So many things affect the creatinine. Hydration, muscle loss, eating cooked meat, low blood pressure, low heart function etc. etc.

If it is clear she needs dialysis, I hope someone comes on with experience, but first I would wonder if that creatinine drop is real, and also why it dropped.