I use an Invacare MKIVA joystick on my power chair, and it slides back and
sideways, sort of under the armrest, so that I can get close to tables.  My
manual dexterity isn't affected by the CP, though, so I'm not sure if this
would work for Amanda.  It has a pretty small nub.  Also, have you
considered replacing the tables she uses the most with higher ones, that the
joystick could fit under?  Sometimes the more creative solutions are
actually the best and easiest.  Good luck!

~Joy~