Well hello grandma! Aren't those grandbabies adorable?
No milk. You can give her KMR, kitten milk replacer, available in most petstores including Petsmart. You should have some on hand for the kittens anyhow, so you can let mom have some occasionally. A couple pet food companies also make little cartons of milk for cats, those are good for new moms, especially mixing in with their dry food.
No raw stuff. I feed my queens kitten food. The Eukaneuba dry kitten food is excellent. You need to make sure the mom eats plenty of it, so occasionally mix in a jar of baby food or can of her favorite fancy feast. You could mix the dry kitten food with a little KMR too (actually you'll be doing that to wean the babies in a few weeks). I have this one queen who screams at me if I *dare* give her just plain dry food while she's nursing a litter!
Nursing kittens takes a lot out of them, although three isn't too bad. You need to make sure that whatever she eats, she gets all that she wants of it. Always have dry kitten food available, and plenty of fresh water. If you get any diarrhea, call a vet ASAP as she'll dehydrate quickly. Your vet can then discuss with you changing her diet if the diarrhea is diet-induced.