Twilight is a liar. She's been keeping a secret from her wife for years. So when she decides to come clean, Sunset finds that certain truths are better left unspoken.
It can be hard, watching as those you love die around you. But Twilight's okay; like Celestia says, as long as she remembers them, they'll be with her. And she's very good at remembering, so they'll always be with her.