With a fiancee visa you can get a SINGLE ticket
But you will need her passport number to book/confirm it.

When she gets to the point of departure (Manila ?), the airline will
check her passport vs the number you provided (when booking the ticket)

They will also check if she has the relevant CFO sticker to depart.

NB... if u book via a multiple website (opoda, asda etc) they may not ask
for the passport number there and then.
Later, you must contact the revelant airline (BA, Cathay etc), and re-confirm
the ticket & give them the passport number.

Hope this helps