It would likely be more expensive to convert things to a traditional floor mount, but maybe not. There is no reason the carrier can't be moved, but you essentially have to strip the wall to gain access, move everything, the reinstall the wall covering.
Either operation is possible, but depending on access and the tile work (which would need to be patched regardless) could add a fair amount to the price.
A floor-mount, rear discharge wouldn't help (I don't think it would mate up with the wall-hung carrier, but could be wrong), but a traditional floor mount toilet on a conventional flange would give her lots more options. Going to a floor mount, conventional flange also may mean tearing up the floor. Not necessarily, as there are tools that can cut a hole in the existing tile there, but keep that in mind, too.