I know you’re angry, rightfully. But take a deep breath and calmly explain to your parents. Try not to interact with your sister at all. I’ll let you decide if you want to give her the silent treatment or just ignore her to an extent. I’m sorry this happened. If you don’t mind me asking, what did she want you to buy for her? And how old is she (you don’t have to give exact ages that’s not the point) is she very young? (0-5) young? (6-9 heh) tween age? 10-12) or teen? (13+) that might give some clearance on how to treat this situation.