For me the fine line between having an affair and polyamory is not fine at all. It's a great big thick line in the sand and it comes down to how much work all the parties are prepared to put in.
The label "primary" is controversial here but there is no other word to describe the relationship that basically holds the nuts and bolts of your life together. In my opinion if she wants her nuts and bolts held together in a convenient manner she needs to prioritize sorting out that relationship before "cultivating" another. And you my friend need to insist that she does.