We have the same problem with my mother-in-law. It isn't that she is rich and literally has "everything" so much so that she has pretty well amassed the things in life that are important to her, is satisfied and if she wants or needs anything - be it a book, or clothes, or well, whatever, she can afford to purchase it and isn't waiting for someone to give it to her.
Perhaps if she like to travel, a weekend at a bed and breakfast, or pay her travel to visit a sibling or old friend or even you or your family.
Does she have family pictures that need to be organizes, put into photo albums? My inlaws had video from their wedding (from an uncle withe an old film recorder). We had stills taken of the wedding, including guests - many of whom are family now long gone.
It think often, what mothers want is time with their kids, grand kids, or older family and friends.