Morally, I do not feel it is right to give the chickens back to someone who cares so little for their welfare. They were on your property, you did not remove them from hers. Depending on what you feel comfortable with, I would either just straight out keep them, or turn them over to animal control and tell them you would like to adopt them if they are not claimed by their owner within the 3 day window or whatever your local shelter has as a holding period. That is most likely the route I would go, That way I would at least feel like I have given the person the opportunity to get their hens back.