Not knowing her situation I can't describe a modification for the steering but will try to give some advice. If you go to mcmaster-carr.com you can find all kinds of materials to make a modification to the steering system to move it to the right side. Something like a solid rod end http://www.mcmaster.com/#rod-ends/=xarpe8
of the correct size drilled with a set screw could replace the steering handle on the left side. Then use a control cable like http://www.mcmaster.com/#throttle-cable/=xarraj
to take the control lever action under her seat and over to the right side. It will take some solid positioning ends to keep the cable in position . If you look at this and have half a mechanical mind you should be able to come up with something I'm sure. I've made all kinds of adaptations to accommodate my disability on bikes, wheelchairs, my truck, etc.
As for putting the drive pedals in I would think a lever system that has a vertical leg on one gunwale high enough to allow the pedal system to dangle over the hole in the cockpit. With a long lever the drive could be raised and lowered with just your right hand once the drive has been attached. Use aluminum such as the I beam http://www.mcmaster.com/#aluminum-i-beams/=xarvww
. to hold the drive you could use something like a clamp to hold the unit while positioning.
Hope all of this gives you some ideas.