You wish for yourself to instantly transform into a girl. With a poof sound your body and clothes completely change, you are wearing the same clothes as Jill and look just like her, but with D cups instead of B cups. She looks at you with a mix of amazement, surprise and horror on her face. "Joe, what happened? You look like me!"
"I don't know" you lie. "But suddenly I felt a weird feeling throughout my body and next thing i know, I've become you!" Jill looks down at your breasts and says "why is it that we look the same, but have different size boobs?"
"I have no idea."
"Well we should get you fitted for a bra, and then you should come to my house, i can give you some clothes." You are a little surprised that she is so accepting of your change but you realize how close you were and that she would probably see it as a way you can get closer to each other. After you got fitted for a bra you found out exactly what size your breasts are. 36DD. Afterwards you go to Jill's house. "Um... Mom, Dad, Iris, you won't believe me on this, but I swear it's true. The girl who looks like me is Joe. He was transformed, and we don't know why so I thought I could give her some of my clothes."
"So you have a twin sister now?" Jill's little sister Iris said.
"Kind of, I guess?" Jill answered in an unsure manner. You go upstairs to Jill's room. She gives you many articles of clothing, but your favourite is a yellow dress, you don't know why but you feel drawn to it. You decide to sleep over with Jill so you can learn about being a girl more.