You'd forgotten that Celestia basically was a super mom to you. While you'd been made aware she always had a somewhat motherly approach to her subjects, something about you had apparently clicked off in her head, triggering even more intense maternal instincts that made her overprotective of you. It was kind of annoying, but also kind of hot. Like getting hit on by a friend's mom, only this time you didn't have to worry about the police taking her away for sexual abuse of a child and earning the absolute scorn of your friend.