I'd say that a lot of secondary characters deserve a lot more criticism/have a lot of negative traits that we usually overlook because we are more focused on analyzing the main character(s). Some people who are written to be heroic and righteous sometimes do some things that is completely out of character, but we generally forget about it quickly because it wasn't too important.
I haven't read LOCH in a while, but would you consider Mu Nianci as shallow, stupid, or just plain naive? She fell heads over heels for Yang Kang which is fine, but she also seemed to forgive him for way too many things later given her own upright nature and upbringing. Did she only love him because his first appearance was a handsome, powerful, bad boy? Again I'm not trying to overly criticize her, but she is generally thought of as a good and sympathetic character, and I'm wondering if she should be also thought of as shallow, naive, and somewhat unfilial in her love for him.