Hi, what are the best documents to prove a legal status in the states other than the naturalization papers? Mother immigrated to US in 2006.

Applied for I-817. Got denied based on sending my mother's naturalization papers instead of sending other paperwork to show my mother's legal status since she moved to US and had a green card issued on her date of entrance in the states. Should we apply for motion to reconsider and send other paperwork (what papers?) or should we apply for an I-817 again? The options given to is on the letter from the immigration office gives us two options: either to apply for another I-817 or complete a 290-B to reopen/reconsider the case.