Because she no longer trusts the car basically, and where fo you stop ?
Do understand what you are saying but I've been in the same position and as she does do some long journeys she needs to feel she may be driving the car back

Yes I do realise buying another is the same risk but ......................................
whats not to trust once its repaired?
you could buy a "new" car tomorrow and have exactly the same issue, the only thing is you wouldnt know. at least youd know the current car is fault free.
fact is cars are mechanical so theyll all break sooner or later.
my history goes something like:
998cc mini - had fueling issues, then crashed it
1.4 saxo - had alarm issues, then crashed it (see a theme, typical young male)
1.2 maestro - no issues, then crashed it (not my fault this time, damn shogun)
1.6 8v saxo - radiator leading to head gasket, numerous suspension issues
1380cc mini - no issues, then stripped it down to rebuild, then sold
1.4 205 - had major fueling issues
1.9td fiat tempera - clutch failed, clutch master cyclinder
1.9td 306 - would randomly stall, always smoked badly when cold, then dropped a valve through a piston
1.9td 406 - egr fail, rear brakes siezed, brake servo, clutch failed
1.9td mk4 ibiza - suspension issues, split turbo pipe, lots of CV boots, immobiliser issues, interior fan failing.. so far