Editor’s Note: One of the founding mothers of the "chick lit" genre, Jane Green is the author of ten novels, which include several New York Times bestsellers. Her latest, Dune Road, was just published by Viking.

I love my friends. I know my friends love me. Most of the time, we don’t see one another nearly as often as we’d like – school events, kids’ activities, work commitments – but every few weeks or so we’ll get together and congratulate ourselves that the mark of true friendship is that it is still easy, still fun, still as relaxed as ever.

Life gets in the way, but the odd phone call to say we’re thinking about them feels like enough, the funny comments we post back and forth on Facebook, and if we have to cancel, well, that’s OK, because we’ll do it again soon.

Three months ago I couldn’t sleep and wandered around restlessly before switching on the computer and checking my e-mail. There was a message from one of my friends. She is someone I consider one of my best friends.

Once upon a time, when our children were in preschool together, we saw each other every day. As couples we went out for dinner all the time. If ever I had a problem, she was the first person to whom I would turn, for she is calm, and funny, and wise.

These last few years, as our children have entered elementary school, and our lives have filled up with their activities, we have seen each other less. Not for any reason other than busy lives, and when we meet for lunch, we always say we should do this more often.

The e-mail said she had been diagnosed with Stage IV breast cancer that has metastasized. She was not ready for phone calls. Not then. She was gathering her family close and taking steps to decide what treatment would be right for her.

This was at the beginning of March. Almost three months later, I have had to re-learn what friendship is. That it isn’t enough to pick up the phone once in a while, or meet for lunch when both of your schedules free up.

Three months later I am learning what love really is. That it is my friend’s brother, who spends hours every day on the Internet, researching, finding out things that even her oncologist doesn’t know. Her brother has become her advocate, her chief researcher, the one who ensures they are on top of everything medically.

Love is S., who goes to every doctor’s appointment, and fights on behalf of our unwell friend, who is too tired, after weeks of radiation and chemotherapy, to fight for herself.