Lucy says fis

This morning, I was showing Lucy a goldfish picture.
I said, " Lucy look there is a pretty fish here."
Lucy went to show dad, " dad, look there is a very pretty fis here. "
Mum, " Lucy fish"
Lucy, " fis"
Mum, " No, fish"
Mum thought she still can't pronouce sh, it is quite cute actually, " Yes, fis" .
Lucy , " No mummy, fis"
Mum wanted to tease Lucy now, " Yes, my dear fis"
Lucy was quite annoyed, raised her voice " No! mummy, fis!"