Just because there's a knee lift lever doesn't mean one has to use it!
I have Berninas that all have the lever and I have found over the years that I have quit using it. I operate the foot lifter like they were done years ago, with a lever by hand on the rear/side of the machine, no problem.

Jan in VA

I haven't used mine either. I tried to learn how to use it, but never got the hang of it. There are a few times I would like to use that function, but not bad enough to go through the trouble of learning it.

If its in a cabinet or you could possibly modify a table and take the presser foot and mount it on the left side of the desk or table, at knee height like they used to be in the older cabinet. I know for my machines, the knee lifter does different things, one it only lifts the presser foot but doesn't make it sew so make sure if she gets one that it does what she wants.

My first sewing machine was an second hand industrial machine and the knee lever was the "gas pedal", I tried to use it the same on new machine, did not work! Lol! It is just faster to use the hand lever to me too.

I don't even use my knee lift. It really hurts my thigh. Don't know whether it's because I'm on Coumadin or not.

Lots of good suggestions here, but if she still wants to use the knee lift, take her and the machine to a machine shop, show them the problem. They will take measurements, and customize one for her. Be prepared to pay $ Rates are not cheap. They may give her a deal though or barter with her. She could make welding caps or ????? in exchange??? Just a thought.