It's natural for a hen to brood eggs this way, and to raise them on her own. She doesn't need food and water nearby. She should return home once a day to eat and drink, if her instincts are good. The exercise will be good for her. I wouldn't do a thing, since it's your neighbor's decision to leave her where she is, and it's his chicken. If she can't get to his food and water, I would put some out, but not hear her nest. I'll bet she is finding her own food and water source, even if she can't return home for this.