Lots of people have faced this situation and most have been able to fight it successfully. Katie's suggestion is excellent. If you cannot get the help you need locally then try contacting Alley Cat Allies directly. They have a small staff and work with cases all over the country so they aren't guaranteed to be able to help with every case but they have gone to bat for caregivers in many, many cases just like this.
However, first and foremost the caregiver must have all of the cats sterilized and vaccinated. If she does not then she doesn't have a leg to stand on. Feeding stray cats who are not spayed/neutered and vaccinated actually does pose a potential risk to public health and safety not to mention pretty much inevitably creating a public nuisance. But if the cats are s/n and vaccinated, then the caregiver is promoting
public health and safety. She's doing what should have been the Department of Health's job in the first place!
Here are some must-read resources:http://www.alleycat.org/resources_care.html#1http://www.alleycat.org/resources_care.html#6http://www.alleycat.org/resources_care.html#12
It's a ton of material to read but there is a lot of important information and the more knowledgeable a caregiver is, the better!