The brunette singer admits she gets so angry she wants to lash out at people who criticise the 'Newlyweds' babe.
She is quoted by Britain's Heat magazine as saying: "When I read somebody saying something about Jessica, I want to kick them."
Meanwhile, Ashlee recently admitted she struggled with an eating disorder as a child.
The 'Boyfriend' singer said her parents took drastic action as soon as they noticed the problem.
She revealed: "I was about 11-years-old, and people in the dance world were really concerned about their weight.
"But, as soon as my parents saw me really skinny, they put a steak in my mouth."
Ashlee now loves her womanly curves. She said: "I think I have good curves and they're womanly.
"I think it's sexy not to be a bone, and it's sad when people get too weight-conscious and don't look in the mirror and see themselves as being as beautiful as they are."
Hear that, skinny girls? ASHLEE SIMPSON DOESN'T THINK YOU'RE SEXY. Heartbreaking, right?