I get the feeling that neither B nor K is involved, mainly because they'd be too obvious. I could see making it obvious to the person being stalked who you are, but not to outsiders. I tend to look at things from odd perspectives at times, but to me it seems more like it was a fairly close friend of hers, who wanted to be closer.
I could see it starting out as just trying to scare her a bit so she'd come to you for "protection" and/or someone to talk to about it. If it didn't work because she turned to someone else, it could have just escalated to the point that neither Morgan nor the stalker really knew how to stop it (not that the stalker necessarily wanted to stop.) He/she could have finally just given up in frustration, and offered her something to take one night to "help her get a good night sleep" and just ended it.
It would be easiler to look at who she actually did turn to, which sounds like maybe CA and CO a lot of the time, but I feel more like it was one of the friends that she didn't turn to. As always, this is totally MOO and could be totally wrong. :waitasec: