I used an old freeware app called "Morpher" to generate in-between frames between each of the drawings, then stitched the movies together in Adobe After Effects. Unfortunately the morphing program created a artifacts, especially between the frames where Kate is opening and closing her mouth. So, I went in and drew over each of the frames by hand to clean up the artwork in Photoshop before stitching the entire thing back together in After Effects. While the final werewolf form's design changed somewhat in the end, the overall animation holds up pretty well.
I later reworked the frames from this animation to create this finished version:
Wait until you see the retouched version... I was inspired to revisit it after posting this. Turns out After Effects runs waaay faster on my new machine, and it made completing the new version (after being on hold for 8 years) a whole lot easier. I'll probably post it at the end of the month.