I too wondered if in fact the coffee was not tainted in some way, I am sure KB threw it away, who drinks something that a stranger brings to your door, not many would do that.
The last Sam tweet update on Friday does state by WP PD after thanking those involved in the search that they are looking for KB's remains.
I remember reading somewhere early on that KK and her aunt had gone out for a beer on TK day in ID, but I can't find it now to link here. Maybe she already knew KB was gone, and was out in ID to make sure she was seen by many people, in case PF tried to pin it on her. I don't think either of them trusted/trust each other %100, the whole honor among thieves thing. All imo