Bella slips into the school by a side door; she just saw a thing and she thinks she's seen it in a book before and thinks it's supposed to be mostly harmless but before she wakes Giles up over probably nothing or kills a likely neutral demon she wants to check.
And she pushes into the library.
"Mark? What the fuck are you doing here?"
"He's an embarrassment on a number of levels and I've only known about him for a few months - Mark, what's wrong?"
"My soul. Mark has detected the loss of my soul and accurately guessed how upset I am about it and now he's equally upset but worse at hiding it."
"Mark is non-literally psychic, he can just guess what I'm thinking with surpassing accuracy at all times. Normally I do a pretty good job of guessing right back."
"...Okay. Well. I've been kidnapped and drugged but I think I can walk now, so if nothing's lurking in ambush outside I want to call my dad and check on my Watcher."
"The question was something like, 'am I currently a more functional implementation of Miles than you are, and if so, what should we do about that?'," elaborates Mark.
"Mark can not only guess what I'm thinking with surpassing accuracy but also use that ability to flawlessly impersonate me. He probably is a more functional implementation of me-with-a-soul than I am, right now."