my cat loves milk

I have always given my kitty milk, i never knew not too, as that is what my mum always did. I have only just found out that cats are lactose intolerant. My puss drinks about 3 cups of milk a day, and she would have more if i let her. She is not over weight, and I have just started buying her cat milk. How much is a good amount for her??

It should say on the side of the carton how much to give. Mine get less than a 1/4 cup to share of lactose free milk (people milk) once or twice a week.