It's not that Raoul's not a great guy. He's just not the right one and, if they're honest, they both know it.
He doesn't go to her performances anymore. She tries not to get dragged to his parties. She feigns ill,
and he knows it's all an act. They still call each other darling and angel but after all this time neither one
is quite sure why they still pretend. Perhaps because it's unbecoming of a gentlemen and Christine still loves her friend too much to shame him. Perhaps it's because she has no one to go to and, at the end of the day, nor does he. Or perhaps it's out of habit. Perhaps it's because five years later they wouldn't know what to do without each other. Perhaps it's because they're all each other has left. She would've been happier with Erik and they both know it. But that ship has sailed, and they know that, too. They are unable to have children, as they discovered in their first two years of marriage when they were still under the impression they were in love. Society is all that keeps them together. For a viscount and countess society is enough. And though being with Raoul isn't bad, though they are dear friends, though they enjoy each other's company, she can't help longing for the life she could've had. Though they can talk to each other about anything, though they still have conversation over the dinner table, he hates that he ruined it for her. They are friends, but both know that's the wrong kind of love. But they cannot divorce for they have no one but each other. So they settle for the easy friendship they have always had. They settle for the companionship they find in each other. They both know they're settling.
But the sad truth is: what else can they do?