Twilight Sparkle has lied to Princess Celestia; tried to deceive her.

Caught in her misdeed, Twilight needed to repair the damage she had done. Saying that she was sorry and a little groveling should have worked. Celestia is kind. Celestia is forgiving. The fear that Celestia would banish her to magic kindergarten for what she had done, was just that, an irrational fear. It should have worked. It would have if Trixie had kept her big... fat... mouth... closed.

If only she had been banished to magic kindergarten instead.