Seeing how one of you was allowed to hold the phone, and you could get caught if you try it on someone else if they see you, it was only fair that one of you would have to be the first target for this app. You both were in the middle of the bedroom at your house as well, meaning that you wouldn't want to cause a big mess.
Of course, when your girlfriend looked closer at the app, she found that it had a targeting system for transforming other people in the palm of anyone's hands. Your girlfriend wanted to know what the button was for, and then a laser came out of the phone, and aimed at you, causing your entire body to freeze on its own. Your girlfriend didn't know what she was doing, but then found the myth menu, and decided which to click, while she was still using it in her own hands.