Natalie, I am sorry that you had to find out what your friend was really like. This is a hard truth but took something like a shock cancer diagnosis to see where your friendship really stood.
My wife had a friend who was always seeking her ear to pour out her woes p, but as soon as my wife had a serious problem that she needed a friend to confide in, this friend was too busy to listen or always hade some reason to go. It was a one way friendship.

I have one friend, older than me, who it doesn’t matter what I am going through, he will listen, maybe give advice, and always offer to help. He has been through many things in his life but is never too busy to listen, and usually cheer me up with some silly joke or limerick he knows by heart.

For all means, still be there for your friend, because you are a caring person, but don’t expect the same in return. I know what it is like to be apart from your spouse for an extended period, and I do feel for you. That sadness and loneliness can’t just be dismissed.