I think she does think he’s bad in bed. I think she tolerated Mr. Two-moves while the kids were little and now she’s seeing no reason to put up with the boring in-and-out routine with Mr. Clueless (who bumbles thru their life believing if she’s not actively complaining she’s overjoyed, and doesn’t know women fake orgasms to get boring sex over with faster, politely) and had not figured out she resented his lack of attention to their home life and her sexual preferences. Now she’s going to have less kid stuff to focus on and more alone time with someone who care more about his job than her, and is no good at what he’s good for?! No thanks.