Ashes to ashes and dust to dust:
Ashes I'll sweep if sweep I must.
Cinderella originally lived by the fireplace and was treated like a servant, sweeping ashes for the ugly sisters (hence the "cinder" in her name).
I've gored a gourd and found some mice
The pumpkin coach and mice turned into horses to pull it.
In hopes that my wishes will end in rice.
Rice is traditionally thrown at weddings, and Cinderella was hoping to get married. (Thanks to the OP for clarifying this clue.)
The clock tick tocks, the time is near
When all my dreams shall disappear.
She can only stay at the ball until midnight, when all her magical wonders disappear.
Who am I? There is one answer true;
Answer fits clue as a foot in a shoe.
The prince discovers her because her foot fits perfectly the shoe she left behind.
This was an easy riddle, as you thought (as evidenced by the answer posted less than 2 minutes after the riddle), but not too easy. It was the last line that put me on to the solution; the first two lines made me think of a brush, and I didn't immediately connect the dots between the other lines, but the "foot in a shoe" bit was obviously significant and made the solution pop into my head.