As you said she has a birth certificate and a passport....
I don't see a problem there.
Ideally you should marry her in Philly, apart from the fact it will be a hell of a lot cheaper than overhere, it will save you one lot of visa fees.
The ECO will concentrate more on your own circumstances than your fiancee/wife's.
You will have to supply proof of income, accomodation, receipts of having visited her,maybe chat logs, phone cards, etc.
All she need really would be small things compared to your lot of documentation.
Welcome aboard and good luck..
