It can be difficult to find just the right gift for someone who is elderly. Even if they are not infirm (and thanks to modern medicine many people are vigorous and active well into their hundreds), they might either live in small spaces with little storage or they have already had eight decades to accumulate everything they want. Give your mother a gift she will truly appreciate; spoil her with "consumable" treats she will not have to dust, launder or put away.
We never outgrow a sweet tooth, so if your mother loves candy you're set. Skip the bagged "assortments" and the penny candy, though, and splurge on her by buying the good stuff that she won't buy for herself. Give her a big box of designer chocolates (no nuts or caramels, if she has problems with her teeth) or a gift certificate to a mall candy store so she can pick out exactly what she likes. Truffles and chocolate-dipped strawberries, cherries or blueberries are also well-received. There are stores online that sell old-time candy, too, if she has a childhood favorite that can't be found any more at the neighborhood grocer's; you may be able to find a "real" 3 Musketeers bar (with chocolate, vanilla and strawberry nougat) that will transport her back to her girlhood.
Find out where your mother gets her hair cut, colored and styled, then make pre-paid arrangements with her favorite stylist to "do" Mom's hair once a month (or once a week) for a year. If she doesn't have a favorite salon, give her a gift certificate good for a manicure, a pedicure or a massage once a month. If your mother doesn't drive, arrange for a cab to pick her up, drop her off and bring her home as part of the gift. She will love feeling pampered and beautiful without having to worry about the expense.
Whether your mother keeps her home neat as a pin or is anxious because she can't get around anymore to clean as much as she'd like to, she may love a once-a-month visit from a cleaning service. They can do the deep cleaning while you take your mom to lunch, and her back and knees will thank you for it. You can also make arrangements for gourmet meals to be delivered to her home daily, once a week or monthly. She will love having someone else do the cooking, and you can be sure that she's eating right.