If you want the babies to hatch, I'd let her finish brooding. But I'd pour a pile of grain on side of nest and put a dish of water as close as possible to nest. I believe she will slip off nest to drink if no one is looking.
I once had a goose die while brooding. Not sure if she starved or did not get enough water. But from that point on, if I have a broody goose not properly caring for herself when broody, I will either bust up the nest or bring food and water to her nest.