If the various boards and groups I've found are any indication, the most common new denture wearer seems to be women in their mid 30's to early 40's but I doubt that is anywhere near the average. Most new denture wearers are likely to keep the fact secret even in an anonymous forum such as this. On the other hand, many people have no idea that forums and groups such as this even exist. I don't know what the average is but I think it's much lower than most people would think. An interesting fact I found is that there are quite a few children who wear dentures due to genetic defects or oral diseases that are out of their control. Sad but true.
You don't mention anything about your mother's situation so the only advice that I could give your mom at this time is for her to make sure that she believes getting dentures is the right solution to her dental problems. If she has any doubts it's best she have them now because once her teeth have been extracted there's no putting them back. The healing process is long and it takes time to learn how to adapt to dentures. Gettng dentures is more a journey than an event. As with most journeys, they need some advance preparation. It will be a major change in her life. One other thing that comes to mind is that she shouldn't be afraid to ask her dentist questions. Write them down and make a list if need be. Dentist don't seem to volunteer much information to their patients.
I hope this has been of some help. There is a long thread on this board that a few new denture wearers here considered useful. It may give you some insight into what a person goes through in getting dentures. The thread is "Immediate denture wearers...please help" started by Scaredstiff70.