Well, in fact the scene with Myriam as a dom, is accessible as long as Myriam is not still dominated by Marc, so the range is wider, which will give more access to make Myriam become more dominant. But on her 'Willpower', even if its high, you always have to keep in mind where Myriam came from, it's not easy to go full confident dom when you were a sub abused for so long, the spark is here and the will to change, but there is still some doubts that can happen, which will take some time to fully disappear.
But of course, she can still have the choice to avoid this scene altogether from the start. ^^