Oh, Linda - I'm so sorry. And empathetic. I had a similar situation w/ a dear friend. Not an online friend but a music reviewer I'd come to know beyond my gig as a publicist for an orchestra and other arts organizations. We'd communicated mostly thru emails but sometimes in person. Anyway, I loved him dearly. He was determined to beat his cancer too. One day, I got a text. Oh, I thought. It's Bob.
It wasn't. It was Bob's phone. Message: Bob died.
I still remember the Shock. Sobbed and sobbed that day and was a waterworks at his memorial.
Again - I am so sorry for your loss. Online friendships are Real. I have lost two Medium friends to sudden death. It HURT.