I know that this is an old post, but I just thought that I’d throw in my two cents.
I had a situation that could have worked out in a similar way. I have a 20-year friendship with three women. We were besties in HS and college, but we’ve grown apart since. One woman, my Maid/Matron of Honor, is the closest of these friends, and we’ve grown closer since I asked her to be my Maid/Matron of Honor. At this point, I can say that she is my best friend.
I also have a newer group of friends that formed in the past 4-6 years. My history is shorter with these women, but they know everything about who I am now. One woman in particular is a really close friend–on par with Maid/Matron of Honor, but she often has “drama” in her life. There is always stress at work, with her family, in her relationship, etc. She was a Bridesmaid or Best Man in another friend’s wedding a couple of years ago, and she confided in me regarding the stress of being a BM–the expense, the relationships with the other BMs (who were all part of another group), the expectations, etc. Let’s call her Friend B. I should also note that the bride is this situation was super low-key and sweet, and this Bridesmaid or Best Man situation was not abnormally difficult.
When it came time to choose BMs, I had a very difficult time. I knew that I wanted Maid/Matron of Honor as Maid/Matron of Honor, so I knew that I would hurt the other two friends from that period of life had I not chosen them. I also knew that it would be strange not to ask Friend B, but I knew that I couldn’t ask the other three women in that group due to bridal party size constraints, and asking Friend B might hurt them. I was on the fence for months.
Eventually, we discussed the situation. Like @luckystar52, I was honest with her, and I told her the reasons that I did not choose her. I also affirmed our friendship, and explained how difficult the decision was for me. My biggest concern was her feeling like the odd-man out in the bridal party of three friends with a long history. I also didn’t want her to deal with expenses like Bridesmaid or Best Man dresses, etc.
What I did decide to do is ask her to write/read something during the ceremony. I do want her to stand up with me, and she is a talented writer. I think that she is excited (although a little stressed) about this task. My impression is that our friendship is still strong.
Being a Bridesmaid or Best Man is an honor, but it is also a possibly expensive and stressful job. I wanted to give Friend B honor, without giving her a job that could cause her stress, and yes, cause me stress in turn (it was combination of selfishness and practicality).
I get luckystar52’s desire not to have negativity. Weddings are stressful enough without BMs adding to that. Luckystar52, it sounds like your relationship is beginning to heal at this point, but I would suggest really having a good conversation with your friend. Really affirm her importance in your life. If possible, give her a wedding job that would make her feel special (but make sure she doesn’t see it as a pity offering). It sounds like you don’t want to lose her. I don’t think that asking her to not be a Bridesmaid or Best Man is tantamount to ending the friendship.