you poor girl , I know how it feels . The same thing keeps playing in the head and you dont get peace . The first thing is in a calm mind approach your sister . Tell her abt it . Its natural if she gets angry ,Be calm . As when we make mistake we should also be brave to face the consequences . Tell her how bad you feel about the wallet also .
A lot of things happen in life .Sadly Its not a game where we can go back n undo things . We just have to learn from the mistakes . Be careful with wallets anymore . And try to forget abt it and stay happy. Thats what matters . Take your sister out and both of you have an ice cream π !