Mama cat has red & tender teats. She just lost her kittens to good homes all on the same day. What to do?

This cat belongs to my nephew who lives with my mother. I took 2 of the kittens and someone else took two. The kittens eat kitty food and mine are doing great, meaning they have adjusted to their new home and have bonded with us. However, my mother says the mama cat cries a lot and goes from room to roorm presumably looking for her babies. They are 7 weeks old.....What should she do?