Your argument is based on incorrect assumptions:
note that a)her husband and rav know that she covers her hair this way (dan l’chaf zchus – you must assume this for a stranger) and b)she is following her husband or rav’s opinion, even if it is wrong (again, you must assume she is following an opinion because of dan l’chaf zchus combined with the knowledge that there are rabanim, even if wrong, who say that covering the hair less than fully is fine). There are entire communities whose rav does not correct them on this (again, I’m not saying it’s right or wrong, I’m saying that they rely on their rav).
Firstly, I’m not limiting my issue with hair covering. It is much much much worse and more than that. It is dressing with the knees and above showing in public in the street (either the hemline is literally above the knee or it is short enough to rise above the knee when she walks, goes up stairs, goes into a car, or other routine daily activities); it is dressing in very tight clothes; etc. And even as far as hair, very often more shows than any shitta ever allows.
And her husband, yes. And he is almost equally guilty as she is, especially if he is taking no action — or worse, encouraging — her illegal behavior.
Her Rov, possibly or probably not. (Being dan lkaf zchus he doesn’t know she is sinning.)