After being her foal-sitter and friend for a long time, she sees Twilight as the filly she'd love to sit for the most. They both love and care for each other very much, even to the point of them sharing a special song and dance. In the Fanfiction A Party to Either Remember or Forget she was so crazy on trying to impress Twilight by giving her the best birthday ever.
After Twilight convinced her to help him, they became close friends. Mickey helped her and Twilight learn how do disolve and befriend blot creatures.
Since the Shadow Blot was the one that dragged her and Twilight into the magic book she immidiately thought of it as a mortal enemy.
After being trapped in his lair for no reason and working with the Shadow Blot she thought of him as a true enemy.