When I bought a house for my formerly ferals, one of the "neutered" males turned out to be only half-neutered. Long story much shorter, before I finally got them to take out the 2nd testicle, he did all he could to get outside to find unspayed females. Also, I was letting everyone out on the...
One other thing I just thought about: have you figured out how you're going to access the kittens to make sure they don't grow up feral? I guarantee she's not going to allow you to pick them up. I'd think she wouldn't even consider letting a human near them until she gets to the point of...
I've trapped hundreds of ferals in the last 15 years. It's very rare for them to eat much, if anything, the first 2 days. Sometimes it's 3 days. I'd say probably 80% of the females I've caught were pregnant, but I trap at night and have gotten every one of the spayed or neutered the very next...