Scared of heights - cog doable?

Look those routes up on you tube
You know your mom's level of acrophobia better than the forum.

Only your mother knows how she might react. I would think that if she looked out to the side of the rail car it wouldn’t be too scary since she would be looking at the same or near level. Looking up the track or down the track could be disconcerting, but even then there is still that connected to the ground feeling.

How does she do on a regular train?

Rack railways will be no more scary than a normal train - unless she gets scared if a train passes over a bridge or viaduct she'll be OK. What you want to avoid is any kind of cable car (Telepherique or Telecabine in French).

Thank you everyone for your great suggestions. This forum is a lifesaver!

I sure don't agree that cog/rack railways are no more scary than regular railways!
People have different ideas of what "heights" bother them. I generally have problems being in vehicles of any type (including cars) on a steep grade.

Heights are definitely a subjective thing, as others have said here. I've gone from being completely unafraid of heights, to doing a steep 2 hour uphill hike and then having a full blown panic attack when I got to the view point at the top. Not fun.

On our recent trip to Switzerland, we had free tickets up Stanserhorn . . . this is one of the cable cars where you can stand at the top of the car. When I first saw it I thought it looked crazy. But I didn't want to pass up this opportunity. Before the trip, I decided it was something I didn't want to pass up. I figured the ends was worth it. Turns out, the guide rail was at neck-height and I felt completely safe.

I live in Vancouver, and ski, so I'm used to mountain tops and various chair lifts, BUT as I've aged, I struggle with heights that I quickly find freaky. I've had many bad height moments, so I feel for your mom. My best resource in these situations is to close my eyes. It makes it all go away. (This also works on amusement park rides --after being terrified after my first Disney Splash Mountain experience, I closed my eyes the second time and it was nothing). Also, remember that thousands of people ride these safely every day. On top of that, the technology in Switzerland is super high tech. Yes, they've had accidents, but overall, they are first class and if I'm going to take one of these anywhere in the world, my first choice is Switzerland.

For example, we took the cable car up Santis in December 2017, and there were 98km/hr winds at the top. We docked without a tremble. Went into the building and couldn't tell it was windy outside other than the changing weather. Here in Vancouver, if we get those sorts of winds, the local cable cars are shut down and they have kindergarten aged school children sleeping overnight at the top of the mountain. A long way to say that the Swiss know how to get up a mountain safely.

In conclusion, know your limitations, and remember the Swiss have the best technology in the world (so it's highly unlikely you'll have an accident), it's not as scary as it seems, and if you can't handle the heights, either look at the ground or close your eyes. That said, if you're going to look at the ground or close your eyes the whole time (as in my 2 hour uphill hike where I couldn't look at the view), it's very much not not fun.

As someone else suggested, show her some videos and go from there.