I know exactly what you AND Bonnie are experiencing... and that is Precisely the reason I still have "my" Bonnie, Lily, Emma, etc.....
The semi-feral ones (especially adults) just don't take change well. It's really sad because there just aren't many people out there willing to devote the time to allowing them to settle in on their own terms!!! Another example is my sweet Boots (tuxedo).
I just need a bigger home with a larger area to keep kitties!