Catherine seems to be amiable enough to the information as payment--it's good to know what's going on topside, after all, when they're all stuck underneath the lake. After Maes explains who it is he misses and perhaps shows a picture of her from his wallet that I assume he has (during this process, she seems to be staring at him intently, like she's listening to more than just his words), she'll indicate that he should go into the curtained side of the confessional as she shuts the door to her side. After a moment, the wall separating their individual cubicles slides open, and sitting across from him will be his wife.

As long as Maes is willing to stay inside the confessional booth, they can interact as long as he'd like. Although it couldn't possibly be the real Gracia Hughes...it'll be incredibly convincing for whatever it is.