Learn me: spin bikes

We ended up getting a cheap one off Amazon. It seems solid enough for her use. I think she's ridden it twice total. 
 

One good things that's already come from it: she's always complained her bicycle seat was too high(it wasn't) because she couldn't reach the ground while seated. No explanation of mine swayed her, and the seat was as low as it would go. 
 

She needs a step stool to get onto the spin bike, and after riding it once she realized the seat being too low isn't good for her knees & asked me to raise it up. Of course I'd just cleaned up her ~10 year old bike with maybe 20 miles on it & was planning to cash in on current prices, but now she wants to keep it...

jimbob_racing said:

Get a used Expresso bike. They're much better quality than anything consumer targeted and with the variable resistance to simulate hills they are a close approximation of really riding a bike.

There is exactly one Expresso bike at the Y where I work out, and it's the only stationary bike I'll ride.  Even so, it sucks next to an actual bike.

If I were the OP, I would lower the dang seat so she can feel comfortable on the bike and put it on a competent trainer.  Your concerns about the mechanics of riding are legitimate, but she's got to be comfortable, or she's not going to ride.  If she takes to it, you can ease the seat up as she gets more confident.