I completely agree that Janet is taking up valuable screen time here in the home stretch. She doesn't have the history on the show to merit it. When (and why) did she get tenure (for lack of a better word)?
In terms of her character, she's a "Holden" type of character. Humble origins, portrayed as basically honest and decent, reacts emotionally to everything, loyal to the point of being blind, stubborn to the point of being completely unreasonable. Unfortunately, she's also a screaming stereotype and really, really annoying.