“Don’t Tell Anyone”

She was my sister’s best friend. Her aunt phoned me and told me that she was very sick.
My first response was, “Oh no! Is she going to be well soon?”
“About a year ago, she was diagnosed, with a deadly disease, but she is doing a lot better,” she said.
I did not ask for details of the disease, but I said, “I am sorry to hear that. I will keep her in my prayers.”
“Thank you. Please do, but don’t tell anyone because she doesn’t want anyone to know. Not even your sister.”
I was upset. How could I talk to my sister, day in and day out and not tell her? Every day, I hoped that someone would tell her. One month went by and my sister still did not know. I was thinking that I should tell her and mentioned that her friend doesn’t want anyone to know, but I didn’t. A week later, her aunt phoned me. She said, “I have some bad news. My niece died this morning.”
“Oh my God! You told me she was doing a lot better!” How could I tell my sister that her best friend died and I knew months ago, that she was ailing?”