What a sense of relief I feel for you. Well done! Sticking with Sissy and caring for her enough to do what you did in order to return her to the shelter took great patience and courage, far more than many others would even dream of. If I was you in that car driving home I would have been 'howling' with tears too. Good for you letting it all out.
I really hope you do hear from them about what health issues she has had going on, and how her treatment goes. From my experience with Snowleopard she was a completely different cat when she wasn't well and behaved very much like Sissy, and yet at any other time she was the most gentle cat you could ever wish for, even wonderful with tiny children and toddlers - even if they hit her or went through mean stages. Lots of good vibes that Sissy gets well and you hear from the shelter about going to see her once she is.
I really hope you do hear from them about what health issues she has had going on, and how her treatment goes. From my experience with Snowleopard she was a completely different cat when she wasn't well and behaved very much like Sissy, and yet at any other time she was the most gentle cat you could ever wish for, even wonderful with tiny children and toddlers - even if they hit her or went through mean stages. Lots of good vibes that Sissy gets well and you hear from the shelter about going to see her once she is.