Suunto makes a decent miniature compass. It's called Clipper and looks like a slightly bigger, more robust button compass. It is better made than no-name button compasses and could be a good choice. You can also attach it to a watch strap, which is a handy feature.

As long as your sister is staying in a familiar environment there is little chance that she would need a compass in the event of a natural disaster. It could be helpful in near zero visibility though (fog, dust or at night), so from that point of view carrying a miniature compass would make sense.

As far as adding a seatbelt cutter, I noticed there is a Leatherman on your list already. Many mid- to large-sized LM multitools have a highly effective sheepsfoot serrated blade. The one on my Wave does an outstanding job cutting cordage and the blunt tip is a good safety feature if used as a seatbelt cutter.