Welcome to YT. I am also involved in rescue and have fostered. Charlie, whom I adopted in 2007 was a rescue pup who went through several homes and his health issues were neglected also. He is still timid but given time, they make the most wonderful companion.
She sounds like she has been very sick, and usually most rescues have health issues that owners didn't want to address. As for the agression, think the advice of other fosters would be helpful. Usually, it is due to fear or pain as suggested.
Good luck and look forward to your future posts. Warmly, Deborah |