Why was this happening?

She could smell the woman's perfume. It was overpowering to her new senses. The cat girl shivered again and rubbed her slim arms nervously as she followed, trying to look into doorways they passed. “Keep up,” the woman instructed, tugging on the leash causing the cat girl to stumble to increase her pace. She blushed as she realised she very much liked the feeling of being controlled.

She found herself walking faster, her small size made it difficult to walk at the same leisurely pace as the larger woman. This caused her breasts to sway noticeably, an unfamiliar sensation for the new cat girl. The woman led her to the end of the hallway where a set of double doors stood. She opened one of them and ushered the cat girl inside. Light streamed into the room and she paused as she saw the man. He looked just like her - her original body! Someone was impersonating her!? They had replaced her with a doppelgänger. A firm downward tug on her leash caused her to stumble and fall to her knees. She looked up in horror as her former body approached.