Kendra, I just want to wish you good luck with the whelping. I know your heart is in the right place, and that you're trying to help. It makes me so sad to think of that breeder keeping her dogs in cages
If I were you, I'd probably end up in jail, because I wouldn't be able to give those dogs back to that person!
I do hope that you'll take all the great advice given here, particularly about protecting yourself with some kind of notarized document. If anything awful happens to the dam or the puppies, I don't think that this greeder will sit idly by. It doesn't sound like her ethics are very good, just my opinion, and I'd hate to see you being sued for trying to help.
Any way you could report her to Animal Control?