If my girlfriend takes a plan b after 1 hour of unprotected sex what are the odds she can be pregnant?

Plan B should work: Taking Plan B right after sex should work, so the chance of pregnancy is very small. One should plan ahead and figure out which days of the cycle are the fertile days, as Plan B would not be needed on occasions when sex was on a nonfertile day (but life can surprise you sometimes). Better than that, use contraception all the time to avoid pregnancy, and to avoid using Plan B except in emergencies.