I'm 'only' 70 , but have fibromyalgia and arthritis.
I bought a light-weight electric weed eater , and find that I can use it quite easily. Maybe that would work for your mother.
I admire her for wanting to continue 'doing' her yard!

gardeningangel,

I'm thinking about getting the one in the link below.

John

Here is a link that might be useful: GrassHog

John,
It looks like the one I got from WalMart.

I'm only 55 - but have physical limitations - Weedeater came out with a new super lightweight, easy to start weedeater that is really cheap and does a super job - I'm very impressed - - - other than that I would recommend an electric one with a long extension cord (but be sure to ask a person "in the know" to get you the right amp for the length of the extension as well as the amp of the weedeater). The electric ones are really lightweight. barb

HI..I have had several surgeries..shoulder,ankles, ,knees, etc and can not manage a heavy weedwacker either..plus I could never start a gas powered ones and electric ones get in the way..dragging cords etc. We just found the perfect thing for me a few months ago at sears.. Its a rechargeable battery powered weed eater. It is great for edging grass around our pool, landscape ties etc. And..I dont have to ask anyone to crank it for me..no smell..no cords..not very loud.. Im well pleased with it..Always starts..easy to use and handle..Might just be exactly what you are looking for.
Hope this helps and Happy Gardening..