Perhaps an orthodox idea, but a split keyboard, like the
ErgoDox EZ, and a trackball between the halves? (or at the side). The EZ is reasonably compact, and the trackball has the advantage that she wouldn't have to move it, thus, it needs less space too.
On the other hand, this setup may be a change too big, all at once. So... a Planck, or similar, perhaps? Though, that may not be the easiest thing to find, especially if you don't want to assemble it yourself.
(Brown are nice, btw)