I agree that everyone has a right to state what they want.
However, I gleaned from the post (though possibly incorrectly) that she knew coming into the relationship-that this wasn't a monoship (she's been the gf for 2 years, the bf has been the bf for 6).
I do not believe she has a right to DEMAND that she get a monoship and her feelings, needs, wants etc are MORE important.
For me-and this is JUST ME-I give priority of responsibility on my part, to the person who came first barring other technicalities that may effect the situation.
So for example, the choice to have another child depends upon my ability to manage that WITHOUT taking away from any current children I have-because they came first.
In regards to poly, neither partner has the right to demand I not have a full relationship with the other existing partner-not even in order to deal with a current problem they are having.
They may request that I alter schedules or devote extra time to them compared to what I have been-but they may not request that I stop having a full relationship with the other. Additionally, they don't get to insist that I begin having a full relationship with someone.
In a situation like this-where my newest partner was demanding I stop having a full relationship with my partner-I would tell them point blank,
"I love you both. I empathize with your emotional struggles. However, I will not neglect or abuse my other partner because you have issues that need dealt with. We can discuss other options or you can deal with them on your own."
BUT-I would also be on guard to terminate the relationship because they knew better. (especially after 2 years)
If my original partner made the same demand-I would tell them point blank,
"I love you both. I empathize with your emotional struggles. However, i will not neglect either of you or abuse either of you because of the other persons personal issues. We can discuss other options or you can deal with them on your own."
I would be attentive for the possibility that the relationship needed to end-because after agreeing to poly, there is a limit to how long it's reasonable (imho) to continue trying to "go back".
My limit turned out to be 3 years. Almost on the dot. At 3 years I quit being open to even HEARING my original partner complain about our relationship being poly. It IS poly. If you don't like it-leave. It's not going back to mono.
"Love As Thou Wilt"