Just turn up on the day unless its changed (which it might so hopefully those more up to date will advise in more detail)
From what i read over the years from peoples posts the process is the same for both. Im sure the Ladies on the site can advise better than me.
370 sounds good also singapore are a good airline from what others here and elsewhere have said/written. If your fiancee is flying on her own its probably better to use a decent airline than one which has longstop overs and maybe not so good a service from the staff.
If your in london might be worth checking with one of the numerous specliaists uk-phill travel agencies based here.