"Well don't." It's not really a question of belief. If you asked what Jane believed she'd be hesitant to share just to avoid the argument that usually follows. It's just a matter of truth, and Jane's unsure whether Arkady's telling it. She's been forthcoming so far, but good liars tell the truth often enough to be believable.

She is selling it though, with that dissociative little outburst of exposition. Jane's no stranger to those herself, and realizes she should probably cut the girl some slack. If she's crazy, it's less a question of subterfuge and more a question of confusion.

"Sounds about right." The description fit Mr. Nobody to a T, and as the rest of the Doom Patrol pointed out, he was about as basic a bitch as you could be with interdimensional powers. "Was he talking to you? Just now?"