You, and Trina finally arrive at the table, where Trina left her spell book, as she grabs it, and starts turning pages to find a hamster reverse spell. You clean a table of dust with a cloth from your backpack, and then place your older sisters uniform on it. "Okay, I found it," Trina says. "Just take your sister out of your ball, and I can use the spell on her."
"Okay, Charlie," You say. "It's time to walk on two legs again." You open the hamster ball, and get your sister out. While she was still a hamster, your sister passed out while you were carrying her all over school. You then place your sister inside the collar of the shirt part of her uniform, where only her head was in. Once your sister was in the clothing, Trina created an arcane blast on her, which caused her to grow back to her original size, and revert back to her human state.
Charlie was fully clothed, and now laying down on the table, until she gets up, and goes over to you. Probably to give you a thank you for restoring her back to her human size, and form, but it's probably not that.