Mona was tired of feeling sick. Sick from marriage then, sick from Desmond now. It took so much of what she had to keep him at bay -- he was a tiger, was Desmond, and listening to the voicemail Lust had left for him only made it all worse. The barrier between the two halves of Divorce was thin as late. Hearing the Sin's voice brought a fresh fight from her other half. So it was maybe not her most clever idea to meet with Lust in person.
Too little, far too late. She took a deep breath outside the penthouse, closed her eyes before rapping on the door for entrance. All this mess, it hurt how they'd come to it. Mona may have always remembered that the Sins were different than the New Gods, but still. There was always a "but". Barring Litigation, Lust and Greed were the closest she'd ever come to kindred spirits. Moreso in some ways, and the thought of how tense and mistrustful things had become between herself and Lust ate at the goddess.
More proof that we should always be alone in the end, Mona thought herself, only clench her jaw at a wave of fight from Divorce's other side. No, she didn't quite believe it, either.