Issabella (your step-mother)

You figure with your sister locked in her room your mother would be the best person to test, as you could see instant results.

You ran downstairs and saw your mother cooking dinner.

"Hay mom, can you do some jumping jacks" You ask without activitating the doll.

"Amor, I'm cooking dinner, I can't right now" she replied your mother was super nice, so you figured she might actually do it without the doll as long as the request wasn't too weird. But you continued with your testing, whispering your mothers name at the doll.

It instantly morphed to look like your mother, wearing her exact shirt, tight pants, and apron. It also looked like it had her figure as well.

"You want to do some jumping jacks" you whispered into the doll, this would make your mother want to do what you said, but without the string you knew she might find it odd to suddenly be compelled to do so.

Nonetheless she walked away from the stove and did a couple jumping jacks and walked back.

It had worked you had figured out how to work the doll and now you could have some actual fun.