Interesting thought.
I am not an instructor or DM, and compared to a lot of folks in this thread I'm a rank noob. But with close to 300 dives in the relatively chilly waters of southern California (plus a few more in warmer places), I like to think I know my way around a 7mm and drysuit. On a few occasions, I've offered to buddy with even noobier noobs who have only ever experienced tropical diving as they dip their fins in our local waters for the first time.
My MO when I do this is very unlike the circumstances in this case. I like to invite these folks to the dive park at Catalina Island, a fairly sheltered, beginner-friendly spot with stairs leading right into the water, permanent buoys with descent lines, and several dive shops within easy screaming distance. You have to swim out a bit to get deeper than 30 feet, and there's plenty to see right there in the shallows, near the bouys and steps; it's a popular snorkeling spot. The water is much clearer than you'll find at most beaches around here.
And still, I exercise more care with these folks than I do with my usual buddy, a dude with slightly more experience than I have. He and I don't really do buddy checks anymore; I might look him over quickly to see if anything strikes me as being amiss, but we're both pretty self-reliant. But with my noobs, I actually go through the whole BWRAF thing out loud, check to make sure things that should be connected are really snapped in, help them guesstimate how much weight they need (I would NEVER countenance anything like the weight Snow gave Linnea), and check in frequently to give them plenty of face-saving opportunities to call the dive if they're not feeling comfortable. I keep a closer eye on them during the dive, sometimes forgoing my camera until I feel good about their bouyancy. And I probably wouldn't offer to do this for someone who was both new to cold water and also using a drysuit for the first time. (Again, it's different with my regular buddy. He didn't take a drysuit course, but I was comfortable diving with him while he figured it out, because I know his general competence.)
If I were an experienced professional, I would be doing things I won't do now, such as teaching uncertified divers. But I would also feel more of an obligation to people diving with me, whether or not they were taking a class at that moment. I can't imagine I would tell someone with Linnea's experience to tag along on a dive like this, unless I expected to supervise her the way I would a student. But that's just my non-professional opinion.