Thank you for what you've done for those foster dogs.
I have been a dog person for over 30 years, showing, training, loving and even fostering. It's really annoying how high and mighty some of these fostering agencies get. They seem to think only they know how to deal with dogs the best when in reality, for most of these dogs, no matter what the situation, a house is better than anything they've ever had.
I think I'd start researching other foster groups who will be more appreciative of what you provide. They should be thankful that you may have discovered a less than desirable trait in this dog that could 'cause problems to an adopter! Think if it was a child or something that set angel off in her new home!