There's a rubric in literature on survival in difficult circumstances (say, being lost in the wilderness) that seems to apply here. And that's that two heads are always better than one.
Even highly experienced individuals, such as lifelong outdoorsmen, make errors that they never would have made if they'd had a conversation with another experienced individual, who would have pointed out the problem. "Never separate" in a survival situation, is therefore a motto. All of us who are trying to execute complex plans (say, a trip across Europe via public transport) can benefit from some other person's input (and there's almost always someone more expert than oneself in at least some of the particulars - can't think of any exceptions to that, really).
Our minds start going down familiar pathways, we're "happy" with our solutions, but that's because our minds skipped something along the way.
IMO, Kaylee had worked at a coffee bar in Moscow. Suspect likes his coffee. Probably can't actually eat out, because pots and pans.
But coffee machines never have had animal products inside them.
How SG would know that BK ever came to that particular coffee shop is beyond me, but SG's mind does tend to make leaps of certain kinds, as is common with many people (me too).