I like wayward’s approach. I think that the way I’d phrase it something like “I’ve been thinking about your comment about losing your best friend at 21. I’ve been a bit out of touch–I don’t want to say something stupid, so could you please tell me who this was. I know you were close to B, but I don’t want to jump to conclusions. I am sorry for your loss.” Something along those lines.
So what happened? Who died?
Bump for an update:
A, the friend now living in the States, posted about the anniversary of her best friend’s death, at 21 years old.
She posted a photo of her friend… it was B.
I haven’t even seen B since 1998, and didn’t hang out with her much since about 1996, but my heart just stopped and I’m crying now. She was so sweet, but so painfully shy that high school was tough for her. She wasn’t bullied much that I remember, but mostly just ignored, which can be just as hard.
I messaged A to find out what happened and to offer my condolences. I don’t know if the news item I vaguely recall was about B, but it kind of doesn’t matter - she still died.
I won’t be posting any details that A might send along - I don’t think it would be appropriate - but I remembered this thread and thought I’d let you all know the outcome.
This sucks.
Funny how we can suddenly miss someone we have barely thought about for years. 
I’m sorry about your loss, mnemosyne, and that it’s hurting your heart.
Thank you for updating the thread.