After initially being totally unsure of what you could wish as a change to yourself, you realize that you are equally uncertain about what you could do to Emma. Whilst you could theoretically wish for anything to happen to her you don't want to try anything too extreme in case it isn't fully reversible. After all, she is your little sister. So you decide to ask Emma what change she would make, if she had the power to do so, and then decide if this is worth pursuing, or just make something up in the way of changes.
So you turn to Emma and ask her the question. After her initial total skepticism about your question, and why on Earth you want to know that sort of thing, she obviously decides to humor you.
"Well," she starts, "first of all, silky smooth legs and underarms that never need shaving. Then nails that never split, and never need cutting. Oh, and that change color to suit whatever I'm wearing. And boobs. I'm supposed to be a girl, and I want a proper girl's figure, so I would wish for decent boobs as a starter. Oh, and I always wanted to be a natural redhead. That enough for you?"
"Is that it?" you ask in response. It all seems quite mundane really, although on reflection these ideas all seem extremely reasonable, and you wonder why you couldn't think of any changes you'd want to make yourself, but your sister can run off a list of half a dozen changes within seconds. "All seems quite reasonable. Do you want to do it all now?"
"What do you mean, do it all now? I can't do any of it! It's just a wish list of things I'd do if I could, but I can't. They're all impossible."
"So if you could then you would?" you ask.
"That's sort of what a wish list is. Yes, if I could I would make those changes, but..."
You interrupt her before she can finish the sentence. "That's all I want to know, and welcome you to the World of the impossible, 'cos you can now have them all."
"Oh bugger off Dan. You're talking rubbish and you know it."
"Not if you know what I do." you reply. "I'll prove it to you..." You reach out and hold Emma's hand with the hand that you'd poured oil into earlier, and still retains the dampness of the oil, and make the wish..."I wish that Emma has silky smooth legs and underarms that never need shaving, finger nails and toenails that never split and never need cutting and change color automatically to match her costume, and that her breasts grow bigger."
"Jeepers Dan, what the heck are you doing? You lost your marbles or something? You can't just wish for thing to happen, you know..." She stops talking for a second. "What the!!!"
Emma looks down at herself, and...