Hi,
There is some excellent advice above. Essentially the UKBA aren't willing to just take your word for it, and they need appropriate evidence to prove your intentions and that the trip is financially viable. The response you got is very typical.
I think you're easiest option would be to reply, with the correct evidence includinlg itinerary, letter from her employer (you can make this and have them sign it), and some information detailing the financial situation. You then provide a supporting letter, referencing the evidence and how it links to the relevant immigration regulations, and also explaining why your girlfriend doesn't intend to remain in the uk at this time and why she has compelling reasons to return to the Philippines.
Good luck.
