JohnnyLs

Typically, the NVC will not require an updated I-864, unless the data in the one from last year does not show that the sponsor qualifies.  The embassy will more than likely asked for an updated I-864 at the interview.
 
I would hold off on updating it.  If your interview is before April 15 2023, you would need to update the I-864 with 2021 tax information.  If the interview is after that date, you will need to include both 2021 and 2022 tax returns.

I assume the I-864 you submitted only showed tax return amounts for 2018, 2019 and 2020?  Unless you also update the I-864, the 2021 W2 is not relevant. 

there's a difference between W2 and tax returns employers have to send the W2 out by end of January (for the previous year) so she would have it 
IRS is slow since 2020 to process the 1040 tax returns 
but if she has done hers,  she can send copy of 2021 1040 with copy of all W2's ,  and other income received 
the USC should be doing this / by your post sounds like  u r the bene
BTW tax date was April 18, 2022 with October if a person applied for an extension 
 
Please do a timeline

Police certificate validity for US immigration used to be 12 months.  But due to COVID-related delays in visa processing, the Department of State recently extended it to 2 years.