Broody hens do not lay eggs so they don’t need layer feed, but it won’t hurt them to eat the layer feed with the rest of your flock for the 21 days while broody; what I do is 3 days before hatch, I put chick food in with her and partition her off from the rest of the flock so they can’t get to it. The chick food is perfect for mom to eat because it contains extra protein to help chicks grow, and also helps mom recover from being broody ( which takes a toll on their bodies ).
However; I personally don’t feed my flock layer feed. I feed all flock with oyster shell on the side. That way I don’t have to worry about my girls getting too much calcium and makes for a much easier transition when integrating - you don’t have to keep everyone separate for 5 months until everyone is laying and can eat the same feed. You can feed them all chick food if you want with oyster shell on the side if you integrate sooner than that.