E&E16

The police certificate is valid for one year.
 
The embassy sent me an email with a list of documents I need to bring to the interview. It says that if a police certificate was submitted to NVC more than a year ago from the day of the interview, a new one needs to be brought to the interview.

Definitely have her go in and ask for it. She will need to fill out a form first. Have her go to the following page, which outlines every detail she needs to know to have this taken care of:
 
http://www.dnrec.jus.gov.ar/Atencion_Particulares.aspx?id=priv
 
You can pay to get it faster. There is an option for 5 business days (common, 70 pesos), 24 hours (urgent, 180 pesos), and even a 6 hour option at select locations in Buenos Aires province (very urgent, 300 pesos). Depending on how fast you need it; we just picked the standard 5 days.

Just as others said, any correo argentino works. Stress that you need it with the 'exception of article 51', I even brought a print out of the embassy's packet 3 that explained what we needed.
 
However All of that and they still got it wrong! But don't worry if You get your police report without the exception, you can file for the correct one online... On the same website that you got your appointment from (http://www.dnrpa.gov.ar). We had to file a complaint on that website that our police report came in without the exception of article 51.  The correct form came in within a few days. 

Okay great! So she should just find the nearest Correo Argentino to her place and go ask for it in person or via phone/ email? How long did it take them to give it to you?
 
Thank you!