I would call Animal Control and let them assess the situation. no animal should be living outside in these conditions, and as is common with most hoarders, I would guess that this woman doesn't take these cats to the vet. At best, they are mating and producing more unwanted litters, and at worst, they are at risk from contracting serious, painful illnesses.

Calling animal control is not always a death sentence, you know. Yes, the number of unwanted animals always excedes the number of homes at any given time, but shelters and A.C. work hard to adopt out all the animals they find. Even if homes are not an option for these cats, a humane and painless end to their life is better than the alternative they are facing. Also, this woman should be monitored against having any pets in the future.

Good luck to you.