Losing a child is the most terrifying thing that can happen to a parent.
Sunset Shimmer had been gone for years. Celestia had never really given up hope that she would see her again, but the doubt had always been in the back of her mind: what if she never returns? The echoes of their last fight followed her all those years.
And now that Sunset Shimmer has returned, Celestia wants to see her again. She has an offer to make, to a filly she raised as a daughter.