Writing a Story for my Niece

Okay so my niece's birthday is coming up and I decided to write her a story. I asked my sister what she thought her daughter would like for the story to be about. She didn't know so I asked my niece directly. It kinda ruins the surprise.Still even if she picked the subject of the story doesn't mean she knows what I am writing about. I hope she likes it. She picked the subject of a family pet she had named Courtney. Now the thing is Courtney died a couple years ago and I really didn't want to make her sad. I wrote like 3 times before I was able to write the story I have now. It's a fictional story. So it's not real. I thought that way she isn't sad when she reads this story. But it can be a way for her to remember her pet.