Originally Posted by ShpaceEchsplorer
What you have done with her boyfriend can only be described as cheating.
I suspect this is the real nub of the issue here if I read the OP correctly. Of course she wants things to work out wonderfully now that they've decided to be honest. That's human. But I suspect she's in a bit of denial when it comes to her own behaviour.
The harsh reality is that her actions have been the complete antithesis of what poly is about. Sure, she might be making some internal shifts to a more ethical relationship paradigm. She may even be using polyamory as a way to justify her own past as it validates the concept of multiple relationships.
But assuming that the GF will somehow be OK with this retroactively is, at best, wishful thinking I fear.