Roxanne,
Treadles can be refurbished and refinished to look really good. It takes a lot of work and time, but it can be done.
I did one a couple years ago that had been used as an aquarium stand. The top was all but ruined. It now looks really nice, and I'm not even an experienced wood worker.
Having your mothers treadle in good running condition and knowing you did it yourself would be a wonderful feeling.
There's lots of how to info here on the forum and we'll always help if you undertake the project.
Joe