This is a strange situation, eyewitness testimony of her own as-yet unimagined behavior. The thing is, she trusts Mulder so inherently; she wants to believe him. And in that way it's easy to make herself the villain-- you're the one who left. But there are missing pieces-- only the smallest of which is that she knows herself, or would like to think she knows herself. There's the lost children-- a great many relationships don't survive that. But it doesn't feel like an explanation.

"You're saying I left because you weren't working?" she hazards, the disbelief evident in her voice. It doesn't sound like her.