I managed to rescue some of my sister-in-law's files without using any commercial software.

At first I tried using the trial versions of the available commercial software, directly accessing the crashed disk. They seemed to work and seemed to be able to find files, but they ran very slowly, so I wasn't sure that purchasing was going to be worth it. I think the problem was that the disk was really badly crashed - it looked as if only a part of the disk was accessible, so the apps tended to 'hang' after a certain point.

So, I then found this thread and tried using ddrescue to copy the crashed disk onto a working disk. I ran it a few times until it seemed to never be making any more progress. Again I never got it to completely rescue the whole disk, as the disk was really bad! Using 'tail -f ddrescue_file.log' allowed me to see that it was working and when it looked as if it wasn't going to progress much further.

Then I mounted the copy using diskutil umount ... (so that the copied disk is accessible in the next step)

Then I used Photorec (http://www.cgsecurity.org/wiki/PhotoRec) to rescue the files from the mounted disk.

Photorec managed to find the same number of JPG files as the trial versions of the commercial software I tried, so in my case I didn't need to use the commercial software. Maybe if I let the commercial trial versions run for longer they would have got some more data off, but I suspect that the disk was too far gone.

Unfortunately, because the disk was really badly crashed, I was only able to rescue a small number of her files, but at least I got some!