It's really good that you recognized there your needs weren't being met and not settling for scraps. I'm sure it took a lot of strength to give her up, but now you know that you would be wasting your time with her, when you deserve better.
Yes! Scraps!! That is the perfect word to describe what I felt was going on. For awhile I thought of the word "replaced," but that never sat well with me, as M did say she loved me (but I see now her actions did not match the words).
Before C was brought in, M and I never had any problems meeting each other's needs. Even when it was just L, M, and me, everyone had their needs met (as best as an LDR allowed). However, when M's needs were being met by someone else, mine took a backseat, not just in priority, but in just being met in general.
Despite all that has happened, I do hope things work out between M and C. My main worry is when M tries to bring another into their relationship and what happened to me happens to their new partner, or worse, C experiences the hell I went through. I don't think M has a strong concept of what a healthy poly relationship is, but also how to conduct a healthy one between all involved with her.
I know I had my own problems, the main one being the problem with viewing things through a comparative lens. But I think being fed the relationship table scraps magnified my comparative nature. I feel this was the case, and I hope it was for not only me, but anyone else who may have a similar problem, and why they too are having comparative issues.
In the end, with M, our intimacy was almost non-existent. I felt like I was nothing more than a glorified friend. I hope no one else has to go through what I did, but if they find themselves in a similar situation, my advice would be to take a step back, therapeutic separation if necessary, and reevaluate the situation.
If you see that you are being fed scraps, then your partner is not only not respecting you, but they may not even be practicing polyamory. As painful as it sounds, my advice to them for their own health and sanity is to leave, or end the relationship. It will hurt, but Love is infinite, and if someone truly loves you, they will show it in everything they do. With all this infinite love floating out in the world, they will find someone else who will love them as they deserve.