Keeping a secret from your friends is extremely difficult, especially if that secret could destroy your friendship with every single one of them.

Fluttershy needs to keep this quiet. But with it affecting her moods and behaviour, some ponies are already suspicious. Rainbow Dash demands she goes to the hospital. But Fluttershy refuses. She can't go to the hospital, she won't go to the hospital. Because then they will know. Everypony will know. And Fluttershy will be ashamed, hated. Why do things have to be this way?