Hey sunnydee. I think, though this is all still formulating for me, that I'm the same. The amount of attachment definitely has a lot to do with it.
I am lovers with a woman, 'D', that I love very much, but I'm not in
love with. I respect her, I love seeing her, we have fun, and she's dynamo in the sack
but I know that her love is with her gf. I don't miss her the way I miss someone I'm in love with. I don't feel all gushy about spending my life with her, etc.
Trust and disclosure for me are pretty much across the board. There's not much that 'D' doesn't know about me. I trust her on many levels. I feel safe crying in front of her, being open to whatever it is she needs to express/do/be.
I guess the difference between primary and secondary is how much I'm willing to change my life around in order to be with that person. Hmm, gotta think about that one...