Not wanting to derail this thread too much but I can answer questions.
@Dowser
"It astonishes me that people actually choose this as a career.....How the heck do you cope with that on a daily basis"
People do still choose it as a career because the image is of a career spent swanning round glamorous places looking tanned and beautiful and earning a shed-load of money doing it. They are less aware (to begin with anyway) of the fact that you start your career by paying approx. £100000 for your initial training then spend the next 20 years in a scratchy polyester uniform trying to hide the wrinkles while you fly night flights, weekends and holidays round the world's dodgiest locations.
On the plus side it is exciting and if you want to see the world it is a great career. The earnings are not as much as they used to be (salaries have fallen as air travel has got cheaper. We want our pilots to be safe and professional....and cheap.) but they are still good. I wouldn't earn as much in another job. I am in a position atm where I fly 2 trips a month to places like the St Lucia, the Maldives, Capetown, Hong Kong, Singapore, etc. and stay in a 5 star hotel when I get there. Not too shabby places.
The time zone changes and night flights DO mess with your body. You get used to it, and develop strategies to make it 'least bad.' Your SIL probably isn't treating a flight back from holiday in the same way I would treat a night flight at work. I would sleep in the run up, sleep at every opportunity I can during (we have 3 pilots on a Florida flight. However the Caribbean is only half an hour closer to the UK and we only get 2 pilots for an overnight flight - less rest opportunities here.) and sleep once I've finished work, till I have done the equivalent of a full night's sleep. I also don't go onto local time zones if I can help it, so on a florida flight I would only be there for one night and I would be up at 4 am catching up episodes of stuff I haven't watched, as I will sleep at noon so I am ready for work at 5pm. Your SIL otoh will enjoy the last day of her holiday, be firmly in the Florida time zone, and will be thinking about unpacking/laundry/supermarket shop when she gets back.
As for landing in fog and who actually lands the aircraft, pilot or autopilot, as per hudyerwheesht's query, the answer is very complicated. All Weather Operations (AWOPS) and Low Visibility Procedures (LVPs) are among the most difficult to grasp parts of flying. On a day to day basis the pilot lands the aircraft. The autopilots are highly complex bits of kit that need no interference from outside sources and on a normal day going into a busy airport there are lots of aircraft all moving within relatively close proximity to each other in the queues for take off and landing. ATC and the pilots are able to see each other, the runway, the other aircraft and any possible problem situations in good visibility. This means aircraft can take off and land on the same runway within sometimes seconds of the last aircraft vacating it. Pilots can also adapt their flying technique for difficult weather conditions such as cross winds and gusty weather. Autopilots do not have the finesse for this so have strict crosswind limits. Once it is past a certain (surprisingly low) windspeed the autopilot cannot land. Nor can it land on a slippery or contaminated runway, ie in snow or in extremely rainy conditions where a blunt application of brakes might cause aquaplaning.
In foggy conditions you are right, the pilot cannot see to land. We have various ways of dealing with this. Each airport, aircraft and pilot has a limit to the lowest visibility they can deal with. Sometimes when it is just low cloud we leave the autopilot in to fly the approach until we reach the cloud ceiling limits then we take the autopilot out once we can see the runway, and still land it manually. This means that the high traffic flow rate most airports work with can be maintained. And if it is a bit windy or rainy, or even snowy we can still land. But if the weather is too foggy even for that we use LVPs.
LVPs require that take offs and landings have more time between them, which is why on days which are foggy there are more delays. Even once the fog has cleared there is a knock on effect on flow rate throughout the day. I get passengers angrily demanding why we are delayed when it hasn't been foggy since this morning and not understanding that the airport needs to catch up. Anyway. The way an aircraft lands in fog is that it has instruments that can detect a very fine signal beam from a landing guidance system located at the touchdown point of the runway. The autopilot does only what a pilot can do, which is to follow that guidance accurately down to the ground. But because you cannot see in fog that guidance system needs to be protected from interference, ie no other aircraft waiting to take off can go anywhere near it. Because this slows down flow rate ATC prefer to hold off on LVPs till it is absolutely essential. The aircraft's autopilot follows this signal - it is like the cruise control function in a car in that it does the last thing it was set to do but does not change it of it's own accord. So it doesn't change speed or slow down, it doesn't select landing flaps, it doesn't lower the undercarriage, it doesn't apply the ancillary braking systems such as speed brake or reverse thrust, it doesn't decide where to taxi off the runway. The pilot does all that, even when 'the computer is doing it all.' Without the pilot input the autopilot would just fly the aircraft into the ground at high speed.
I hope that explains a few things anyway.