You shouldn't steal things that don't belong to you.
Ash notices that her sister has a really cute top when looking through the closet.
Ash wants to wear the top when she goes out.
Ash offers to trade a top that her sister likes for this one.
Ash takes the top without asking and keeps it in her closet.
Ash's sister is happy to trade the top as she likes the other one better.
Ash's sister finds out and is furious with her as she was looking for it.