Dude, either take her face off, or accept that her "Conservative" relatives will find their daughter/sister on one of their mysterious porn hunts. Sure, they were looking on the internet for bibles, low and behold, her picture pops up!
If she's unsure, then don't do it. You can STILL make money by taking pictures of other girls that don't mind.
I would take a set of pictures of your GF though.
As a payment... for my advice... yeah.. that's it!