Lynn is not most people; the fact that Anthony is clearly lusting for Liz in his heart right where his wife can see it and if she doesn't like it, she can go to Hell doesn't mean a damned thing to her. That's because Anthony is representing her in this instance; since it's okay for her to flirt in front of her husband, Anthony can thought-bubble away in smug complacency and Therese is just supposed to sit there and take it. It's when the other person flirts that it becomes a crime.
That being said, Lynn's being a self-absorbed hypocrite only explains one half of what's wrong with the caption; we also have to contend with her odd belief that since Liz doesn't mean to be a threat, Therese should know this and chill the Hell down. Most people grew out of thinking "Well, I know that I'm not doing anything bad so why does this person think so?" after they graduate from preschool; again, Lynn is not like most of us. If asked, she'd say in all confidence "HUM! Well, Liz doesn't mean to interfere so Therese is being a picky-face because she knows that Liz doesn't mean to interfere; she's just doing it to be a jerk." The terrifyingly perky expression, girning like a child who can't stop fidgeting and flailing limbs we'd have to watch would only tend to add to how horrific it is to realize that Lynn just does not get how people behave in the real world.