The woman will not be immediately eligible for permanent residency as a result of marring a Green Card holder, so if she goes out of status while in the U.S. she will not be eligible to adjust her status unless she is married to a U.S. Citizen. She can return to her nation of origin and pursue consular processing for her Green Card, which based upon the current Visa Bulletin will likely take a year, or she will need to wait to try to adjust her status until her boyfriend becomes a U.S. citizen. I don't suggest overstaying after going out of status without first discussing your situation with an immigration lawyer.

