They could definitely use a bit more weight in my opinion (some of them anyway), but they are FAR from either starving or unhealthy. And some people like their horses lean. Really, it's a better condition for them then obesely fat especially if they aren't working.
The woman is just deranged. You have nothing to fear, the Humane Society would scoff at her for absolutely wasting their time. They have plenty of food and water, and I don't see any horse in alarming condition. I'd prefer to see a bit more meat on them, since they're lean enough that it would only take a few days of going off feed to see more alarming condition, which is why I like a good healthy weight, it's easier to notice if something changes and do something about it before it's a problem.
All in all though it's your choice, and none of them look starving.