As Spike was left behind at the GGG, he visits parts of the castle from childhood. Runing into Luna, she invites him to the library. As they talk, Spike talks about feeling used and hurt. Luna asks why, Spike tells his story from the beginning.
Spike attempts to comfort Twilight after the events with Flurry Heart when she worries about being the worst aunt ever after the events with Flurry Heart at Ponyville Hospital.
How could she miss it? The seventh element was right under her nose the entire time, supporting her, guiding her, and loving her. When it strayed from its course, destiny itself nudged it back into line. It was always there... It was just waiting.