I am assuming you will marry her and petition her to immigrate as a spouse. The process to get a green card in the US is Adjustment of Status. It is not a problem that Adjustment of Status isn't completed within their period of stay, because once someone has Adjustment of Status (I-485) is filed, they can stay in the US for as long as it is pending regardless of whether they have status or not (and in fact cannot leave the US without Advance Parole, or they will abandon their Adjustment of Status).
(In fact, in her category, she doesn't even need to be in status at the time of applying for Adjustment of Status; she could have overstayed for years and still be eligible for Adjustment of Status. In some other categories, she might need to be in status at the time of applying for Adjustment of Status, but it is true in all categories that she doesn't need to maintain status while Adjustment of Status is pending, and going out of status while Adjustment of Status is pending won't affect the Adjustment of Status.)
Employment-based immigration requires being petitioned by a US company that will employ her after she immigrates. This usually requires the company to go through a complicated process, and companies generally don't go through the effort to petition people unless they are already working for the company in the US. Unless she has such an employer, employment-based immigration is not a viable option.