As a side effect of getting older, you're eligible to have friends that you haven't seen in very long periods of time. Just because you're old enough for that amount of time to have passed.

I was talking to my grandparents a number of years ago and they were talking about some good friends they have. Which they haven't seen in over 40 years. This is sometimes just a thing that happens.

ALSO, 'ask not for whom the bell tolls'. I didn't even know about this person until now, but I still feel bad for her.