Why is it important to tell the OAS what really happens?

The OAS (Organization of American States) is coming to investigate the political prisoners' situation, and Minerva urges Maria Teresa to share the incident she has written down with the OAS. The OAS could potentially help the sisters but at the same time reporting to them could harm others. Maria Teresa decides to go against her sister's wishes and does not give the OAS the letter of her personal account. She explains, "The second note with my story was lodged further up in my braid. Maybe it was the sight of that ribbon Santiclo had given me when I was so broken, I don't know. But right then and there, I decided not to drop the second note. I just couldn't take a chance and hurt my friend."