The priority date is not current for the F2A or F2B (assuming that you are unmarried) family preference categories.
When the PD is current and you are in the U.S. maintaining your nonimmigrant status, the adjustment of status application can be filed.
Is not the answer obvious? How one can seek a benefit without grounds for it?
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You cannot file an application for adjustment of status unless the priority date is current, At this time, neither the F2A or F2B categories are current. At this time, your mother may file the immigrant visa petition.
Please keep in mind that filing an immigrant visa petition gives you authorization to remain in the United States beyond any authorized stay you may have in the country. You must maintain lawful non-immigrant status while the petition is pending. Otherwise, you will be ineligible to seek adjustment of status and risk trigger an unlawful presence bar.
The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter. No recipients of content from this answer, clients or otherwise, should act or refrain from acting on the basis of any content included in the answer without seeking the appropriate legal or other professional advice on the particular facts and circumstances at issue from a licensed attorney. Provision of information on this website does not create an attorney-client relationship between you and The Law Offices of Grinberg & Segal, P.L.L.C., nor is it intended to do so.
Your priority date has to be current. You also have to be maintaining status when you file for adjustment. See an immigration attorney, you don't want to make a mistake.