Why not get her a maid.. Get her out of the house and to a spa for the day and have someone clean the house for her!
A maid is actually the #1 thing she needs the most. And, it would need to be a weekly thing, not just once. Waaay too expensive though.
A year subscription to Netflix would be cool. I love getting movies in the mail and they have a HUGE selection. A year is like $120.
How much do you usually spend on flowers? If you're like me you don't spend a lot, but every now and then instead of buying a gift I blow the entire birthday present amount on a really nice bunch of flowers. Go to a good florist and ask to see what spending $50 - $100 will get you. Chances are if your Mom is like most Moms she would love to have a really big, nice looking flower arrangement. Go for something that has Birds of Paradise in it, those always look great.