Is there any Shari impediment to helping one's mother with cleaning and sweeping at night due to the unavailability of time during the day?

There is no legal impediment to performing day or night work at any time. The questioner should convince her mother of this, for the belief held by some that performing such work at night leads to something disliked is a corrupt belief based on ṭiyarah (superstitious omens), which is forbidden in Islamic law.