Absolutely love this story so far, some of the best forced petgirl fiction I've read. The slow descent into becoming a helpless pet is wonderfully done. I often fantasize about such a predicament happening to myself, but I also understand it would be a hopelessly inescapable prison - something you've really nailed with Lisa's initial resistance and then her slow acceptance of her new lot in life.
I look forward to the next chapters, and I hope you keep writing great stories like this!