Kate's 100WC Week 3

Prompt:

...but how would I know...

My Sister Drives Me Crazy

My sister drives me crazy. Today she flushed my goldfish down the toilet. Her excuse was, “But how would I know?”

We despise each other, but Mum’s oblivious! Once Mum told her “Darling, get you and your sister a cookie”. They were my favourite, crunchy and chocolatey on the outside and chewy caramel inside. My sister purposely put it in the lounge, when the dog was there. She then innocently called, “Dear sister, your cookie’s in the lounge.” When I turned up, only crumbs remained. I went straight to Mum, all my sister said was, “But how would I know?”