You need to petition her for a fiancee visa. The adjudication of the petition should take between 3 and 6 months. In my experience, it takes about 4 months for a consular interview in Nigeria, assuming that the filing was done properly and there is no further administrative processing of the case.
File a fiance petition for her so that she can enter the US within the first half of this year. You will then need to marry each other within 90 days of her admission
Samuel Ouya Maina, Esq. 415.391.6612 email@example.com Law Offices of S. Ouya Maina, PC 332 Pine Street, Suite 707 San Francisco, CA 94104
File fiancee visa it takes approximately 3-6 months. Then she comes her on the K-1 fiancee visa, and you must marry within 90 days. Then, file for her green card here in the US after marriage, another 4-6 months.