Her name is Time.
Although she looks young, she's the oldest one in the universe.
Time is strict and true to her duty. She never looks back but always looks forward to keep things going. When people says 'Time flies', she will shake her head refusing. She never flies. She can only walk steadily in her rhythmic paces.
But if you look closely, you may see a glint of mischief in her eyes. She knows sometimes people take her for granted so she plays with their mind.
When people feel happy, she will quicken her paces so that it won't last long.
And if ones feel sad, she will slow down her steps as if to let them suffer more.
It is not that she is cruel. It is just her way of letting people know
the truest truth.
That there is no certainty in this world at all.