[davekc]

Your most economical way to approach something like this is to approach a fleet owner with a truck to drive. You can both go to the carrier and go through orientation and drive the owners truck as a solo initially. Then you can use that truck for your test.
If she feels uncomfortable, practice in your cheap local rental truck, and then make the move. The fleet owners truck will likely have the air brakes.
I would stay away from schools and paying or going into debt to obtain a class B license.
No need to complicate the simple.