Like it does with all of its models Nissan doesn’t recommend that you convert the Pathfinder to LPG, but that’s because it doesn’t want to carry the can for any problems that might arise because of the conversion. Aside from Nissan’s aversion to LPG there isn’t any real issue with converting the Pathfinder as long as you use an experienced and skilled converter and a recognized system. The system you will find you have to use is the more expensive vapour injection system, which does a good job but costs more. I would believe the Pathfinder would be a good car for your wife if she’s comfortable with the size, but it would be relatively heavy on petrol, and with the mileage I guess she could be doing it might not be viable to convert to LPG. I would consider the diesel.