I wouldn't of said one airport was better than the other, they have good & bad days at each I guess but personally, I prefer Heathrow Airport to Gatwick Airport.
Airlines are all pretty much the same really & incidents are generally few & far between.
Yes, your wife will need a passport & a visa.
Once at Heathrow you can get a train, underground or bus into London, it's a pretty big place but there's plenty of public information boards around & there's a map showing all the different routes on the underground system.
Dollars are not accepted in the UK so you'll need to exchange some of your dollars for GBP if the wife needs cash. If your bank cards are MasterCard/Visa then they should work in our cash machines anyway. Failing that you can either get your English money before you fly or when you land in the UK.
Current exchange rate is 1 US dollar equals 0.82 GBP
Obviously you'll need to book hotel accommodation so you need to decide whether to book a hotel nearer the business venue or nearer to the airport.
Where in London is she heading?
