This is probably bullshit but squawkers are squawking that Jessica Simpson is bullshit because John Mayer mistook a picture of her sister Ashlee for her. Hah! Dude, get mad at your irritating boyfriend. It’s his fault. He shoulda kept his foolish mouth shut if he wasn’t sure. And by the way – Ashlee’s looking better than you. At least more human anyway.

“There’s certainly a sibling rivalry between them,” a source close to the two tells Star. The trouble began, says another insider when Jess’s boyfriend, John Mayer, pointed to a glamorous magazine photo and asked Jess, “How old is this picture of you?” But-whoops!-it was a shot of Ashlee! “Jessica read John the riot act,” says our source. “He definitely touched a nerve.” Her sensitivity on the subject seems to be the direct result of Ashlee’s emergence as a sex kitten, a role once owned by Jessica. That Ashlee has become the hot blonde – a transformation that came courtesy of a surgeon’s knife, a bottle of peroxide and dramatic weight loss- is troubling to Jessica, who has morphed into a buxom and sometimes frumpy brunette due to a dye job and about 20 extra pounds. “Jessica hears the catty talk about how Ashlee looks like her- from two years ago,” says the source. “It totally bothers her.”

Dude, Jessica needs to chill. Ashlee’s hotter now so that means their incredibly creepy father will be focused on her for his wank fantasies. She’s lucking out.