My 77 year old mom has trouble getting to the bathroom in the morning. Should she stop drinking liquids after a certain time before bed? How long?

Overactive bladder. Sounds like oab.But 1st check a urinalysis. Yes stopping liquids a few hours before retiring is first line. Avoiding bladders irritants(caffeine, alcohol, spicy foods)may also help.Next step is considering medication for oab, there are many- side effects also need to be considered when starting this class of drugs, paticularly in the elderly.
Instead. Have her go to the restroom before she goes to bed and that should help, try having her go to the restroom as often as possible before she goes to bed.