We had chickens when I was 4 a dog got in and killed them all when we were out. Dad cleaned it all up and told me the chickens went to live on a farm. I was heart broken, after a few days of being upset dad went and bought another one for me and told me that this one missed me too much and wanted to cone home. I was 4 I couldn't tell the diff.
I don't know if telling her would be a good idea cos she may want to see it too much etc and that wouldn't help with the healing process.
Maybe you could see how it goes and if it survives cone up with a similar story?