Making her get her own breakfast is generally good. I cut Lucy's feed down by a few scoops per week for a few weeks until she was only having 400mls per day, then started only giving her 200 mls at night for another week, then nothing. That was down from a peak of five feeds per day, total of 1.4 litres per day. I could only get PalaStart Lamb and Kid Milk Replacer, not ProviLac Shepherd like I was after, but it did good. How much you're feeding your lamb would depend on breed, history, environment, and formula, and I know next to nothing about your particular circumstances. But it's good to play it by ear in general.
I weaned my lamb late because of the damage of her early days, but generally Damaras are eating grass in their first week and grazing strongly by the second; I could have probably weaned her a lot sooner. My Merinos took a lot longer than that, but I weaned them late too because they were also damaged orphans.