Tonight, I petted Cindy more than ten times. I started to scratch her cheek and she started purring! She did her flop onto the ground and I was able to go with it and keep petting her. I massaged her neck scruff. It was the first time I petted her so much I got tired and wanted to do something else.
This transformation is actually happening! At times I never thought it would.
Video of latest playing: https://youtu.be/u4y_y1CN498
Looking grumpy but doing normal cat things like actually being up on a chair: