Twilight has been showing classic signs of no love sickness. She's tired, bored, and a little depressed.

Celestia decides that just won't do, and decides to find Twilight a mate.

Celestia quickly comes to the realization that she has no clue what sort of sexual partner Twilight would want. Too embarrassed to ask, Celestia scries for a pony who is more... malleable. When that fails, she broadens her search.