Bottle-feeding kittens is far harder than bottle-feeding babies as they don't have a cough reflex at this age. So long as they are putting weight on leave well alone.
Milk as a "everyday matter of fact" is not necessary, true. Food here and milk there, to drink.Milk and milk products are not a natural part of the diet of an adult cat and nor are they a balanced diet for an adult cat. What she needs is as much good-quality kitten food as she will eat.