Ah, GF is really a good girl. Not one to destroy things. More one to back off if she senses she might be messing things up between my fiance and I.
She just isn't someone who is okay being non-primary at all. And I get that. I don't think I could be non-primary with someone and not have a primary of my own. She goes through periods of feeling nice with us and periods about being very upset because this is not really how she pictures her life.