If she has food and water close by, she will be fine. Broodies get up and eat and drink and poo once a day. You just likely won't see her, and might not notice a lot of the food gone. Keeping her on high protein feed is important, and I like to put vitamin/electrolytes in the water to also help boost her.
Ah yes, those darn black ants. They don't seem to bother the hen, but I don't like them either...and they WILL swarm over the hatching chicks as they hatch bringing in bacteria.
I use "Orange Guard" and Poultry Dust (Permethrin) in the nest area to help cut down on them. Neither of those will hurt the hen or eggs or chicks.
Lady of McCamley
Thanks for the info! I have diatomacious earth in the nest box but maybe that's not effective against ants.
I will need to get a feeder and waterer for the chicks so I'll buy that now and put it in the coop close to my broody.