"I wish that you would be a snake hybrid Cathy" You said to her.
Aunt Cathy fell to the ground. As she looked at her legs she saw that her legs began to feel momentarily weak. She was forced to go to her knees for what she expected would be the last time. Her legs drew together, forming a single appendage. Her knees and feet melded into this new appendage which grew in length from where her feet had been. She watched as her breasts grew from C cup to DD cup breasts. Scales formed along her new tail, up what had been her legs but leaving her ass (which was now even more perfect than it naturally was) and vagina. She could quickly by slithering, faster than any snake. And her tail was stronger than any snake's - she could crush any man wrapped in her coils.
Every trace of hair, except for her eyebrows, eyelashes, and the hair on her head vanished, leaving her with perfectly smooth skin.