With friends, it can be really awkward. I don't like overly touchy, feely, flirty friends. Especially when you sense it's not joking but real. It creates an unnecessary tension. If you prefer to stay discreet I find that if you show them with body language (in a critical moment: larger distance, crossed hands etc, combined with a little bit more official tone of voice) they will catch on. If not, you need to say it directly, however you decide to word it. Be sincere. Give them some time to process, since it is a sensitive topic and it might hurt them. If they cannot handle it, well, it turns out, sadly, they aren't really your friend, no matter how cliché it sounds. I know the feeling, I mourned a couple of my own due to different reasons but the feeling is the same. I wished they did something differently so we'd be able to have a real friendship but alas, wishing was all I could do. And getting to terms of loosing a friend.