Cats/kittens are lactose-intolerant!!! Kittens and all cats should NOT be given milk at all. It will only cause them to have diarrhea. Please STOP giving her milk immediately!
Cats, incl. kittens should ONLY be given water. Make sure you cahnge the water 1 -2 times per DAY! Some cats, incl. several of mine, are extremely finicky about their water and will only drink it when it is fresh.
Also - put her water bowl in the dishwasher once a week, to keep germs at bay. No one, including a cat, wants to drink out of a dirty water bowl!