Yes, feeding the momma cat with a separate bowl is a great idea. We do this for our female cat, and she is much less cranky because of it.

When her two remaining kittens were over three months old, she was trying to wean them, but one in particular was so insistent that she would give in and wouldn't wean them.

I did want to get her spayed at that time and the vet mentioned that her milk needed to be dried up for four weeks before the surgery, so we had to separate her from her two remaining kittens for a week. This did the trick. It broke the maternal bond and she was spayed a month later.

Best of luck.