Eventually before the expiry of her visa, she will travel back home.
So she won't be classed as an overstayer, thus making things near enough impossible for a fiancee or settlement visa.
Ideally, you should visit her a couple of times, and collect any hotel receipts, plane tickets, boarding card stubs, chat logs, phone cards, etc. Stuff which will come useful together with photos of you together and with her family once the application time arrives.
The best of both worlds would be to marry her there in Philly.
Various reasons for this.
1 - Family. Pinays are very attached to their roots
2 - Big family wedding means lots of pride
3 - Heck of a lot cheaper overthere, even including flights, hotels, trips, kitchen sinks and carabaos'r us.....
3 - Saves 1 lot of visa fees (around £500)
Lots of plusses and no minuses.
You will find that the vast majority of the members here do agree with me.
Also visit Peters website, a mine of information on everything.
http://www.british-filipino.com/
Good luck