Actually she should have water available from the time you got her! My rex kittens were drinking water from mom's dish from 3 weeks old
Milk is a food - not a source of "water". If your kitten is eating solid foods (kitten) and drinking water, then you don't need the KMR. I think I only used it for a few weeks when they first started eating. But mom nursed them for 10-12 weeks anyway, so I rarely had to use KMR.