There are SOOO many ways this thread could go wrong.....
Actually they are quite comfortable. She won't get the vibration the bike gets for starters. There is plenty of leg room even is she is tall. Here is where it gets tricky to mention.....
The seat is pretty wide too.
The seating is....spacious
Speaking of which, higher end specialist upholsterers like Seat Concepts and Oregon Aero use multiple layers of different types and different densities of foam in varying thicknesses to create seating that is free of pressure spots and comfortable for as long as you can stay awake.
An old school trick my ancestors used in the 1920's to help keep the passenger warm in cold weather, a hot slab of soap stone wrapped in cloth and buckle belted to the slatted wood floor mat.
Today we can use electric heated garments and a spare battery. 12 volt electric blankets are availble too.