This is an STD forum, not a place for general questions about non-STD sexual issus. I am aware that preganancy sometimes occurs without actual penetration, either via pre-ejaculate fluid or because of semen ejaculated near (but not in) the vagina. The risk from the exposure you describe sounds low, but this is outside my area of expertise and I have no advice about morning after pill etc. Your girlfriend should check with her health care provider.
Good luck-- HHH, MD
Despite common belief, newer research shows pre ejaculate itself doesn't contain sperm, but may have sperm in it if you haven't urinated since you last ejaculated. Of course, if you wiped your fingers off before inserting them in her vagina, you're fine either way. Still, she can always take Plan B if she's really worried. Despite the moniker "morning after pill", she actually has up to 72 hours after unprotected sex to take it. It's up to the two of you and her doctor to decide whether this is a worthwhile exposure.
And I'd suggest she talk with her doctor about her birth control options. Why worry needlessly in the future?
Good luck!