My captain is deaf in one ear so even if he hears something 'not quite right', he has no idea where it is coming from. If something is askew and he doesn't notice (rare), it is my responsibility to alert him. I'll yell "trim" if chain is rubbing; "X ring" if the FD skipped; "chain off" if we dropped chain (we'll coast while I reach down and try to put it back on), etc.
Keep asking your stoker 'do you hear something?" if you feel something is wrong. She'll eventually develop that mechanical ear, even if she isn't mechanically-inclined. I might not always know
what is wrong with the bike, but I can tell my captain when something isn't quite right (ie creaking bottom bracket).
For shifting and preferred cadence... that is different. I'm more of a spinner than he is, especially at start of season. If he is grinding it out and I'm not happy with the cadence, I'll slap him on the butt. If he continues to smash through, I just let up (a lot) on my effort. If he wants to smash his way up the hill, so be it, but he isn't going to get a whole lot of help from me that way. I find this to be less of an issue by ride #2 of the season. Having computer that reflects cadence helps him in this regard because he knows where I am happiest and when the butt-slapping will commence.
