Ashlee attended Prairie Creek Elementary. An accomplished dancer, Simpson began studying classical ballet at the age of three, and was admitted to the School of American Ballet in New York City at the age of eleven. Around that time, she suffered from an eating disorder; the condition lasted about six months, and she dropped to about 31 kg (70 pounds) at 159 cm (5 ft 2 in), but her parents then stepped in and got her to eat more. After her sister Jessica Simpson landed a record deal, the Simpson family decided to move to Los Angeles, California, where Ashlee began appearing in television commercials.
When Jessica became a star after releasing her first album, Ashlee became one of her backup dancers. Later, Ashlee began appearing in films and television series, including an episode of the sitcom Malcolm in the Middle in 2001, a minor role in the 2002 film The Hot Chick and a recurring role, 39 episodes from 2002-2004, on the family drama series 7th Heaven.
Ashlee recorded a song called "Christmas Past, Present and Future" in 2002 for the holiday album School's Out! Christmas, later to be re-released on Radio Disney Jingle Jams in 2004 and 2005. In the summer of 2003 she released a song titled "Just Let Me Cry" for the soundtrack of the film Freaky Friday. Eventually, Simpson signed a record deal with Geffen Records.
Previously blonde like Jessica, she dyed her hair dark during the recording of the MTV reality show after she finished filming for the 7th Heaven television series. In November 2004, she debuted a shorter haircut with the same dark color. Following the end of her Autobiography tour, in early May 2005 she moved back to a blonde color; she remained blonde until January 2008, when she appeared with a red hair color.
She has seven tattoos: a star on one wrist, two cherries on her ankle, the word "love" on her other wrist, the number "3" added to one wrist in 2007, and a large peony flower on one wrist in early March 2008.
Simpson and her sister were tied for third on oft-quoted celebrity-fashion critic Richard Blackwell's list of the worst-dressed celebrities of 2004. Blackwell quipped that "from gaudy to grim to downright frenetic these two prove that bad taste is positively genetic."
Simpson's relationship with actor Josh Henderson lasted for nearly two years and was shown ending in the first episode of The Ashlee Simpson Show. Soon after, she began dating fellow musician Ryan Cabrera. That relationship was also featured on the show, and Simpson appeared as Cabrera's love interest in the music video for his song "On the Way Down". The two were reported to have split in August 2004 due to their hectic schedules, but they resumed their relationship for a while afterward, before ending it again in early 2005. Simpson said afterward that they were still friends, although rumors suggested that Simpson did not like the fact that Ryan had moved on to Lisa Origliasso of The Veronicas.
At the beginning of her music career, Simpson said that she would not discuss her sex life, in contrast with her sister, who had openly stated her intention to practice sexual abstinence until marriage. "I decided that I didn't want to talk about that because it's super personal," Simpson said of the situation.
In 2005, rumors began circulating that Simpson was in a relationship with Wilmer Valderrama, who previously was involved with Lindsay Lohan. Simpson's single "Boyfriend" was reported to be about the situation, but she said that the song "is about [how] every girl out there sometimes thinks you stole her boyfriend. It's just making fun of that." Valderrama subsequently said on Howard Stern's radio program that he had sex with Simpson, but claimed the incident was unrelated to his break-up with Lohan. Later that year, rumours arose that Simpson was secretly dating another Joe Simpson-managed actor, Viva La Bam's Chris Raab. In February 2006, she told Seventeen magazine that she was dating bandmate Braxton Olita and went on a 10-day vacation with him to Hawaii.
In November 2005, eTalk broadcast a video of a late-night visit made by Simpson to a McDonald's fast-food restaurant in Toronto, Canada. Simpson appeared to be intoxicated in the video, and was shown arguing with an employee, as well as rejecting a customer's attempt to get an autograph from her because he wouldn't kiss her feet. According to Simpson in a 2006 Elle interview, she was "a little tipsy", and the customer had first called her "gross" before he had realized who she was, at which point he asked her for an autograph. She said that she told herself to "grow up" after the incident.
In February 2006, Simpson was honored by MTV's Total Request Live (TRL), as the "Bounce-Back" artist. The award was given to her for being able to recover from the negative moments of her career and release another #1 platinum album.
Simpson reportedly had a nose job in April 2006. When asked about it in an interview in May, Simpson neither confirmed nor denied it. In the May 2007 issue of Harper's Bazaar, she said that she was not insecure about her appearance and had not been beforehand. She said that plastic surgery was a "personal choice" that one should only decide to do for oneself and not for others. Joe Simpson said of the surgery in a September 2007 interview that "there was a real problem with her breathing and that was cured". In March 2008, she said that "as long as people have two eyes" they could determine whether she had a nose job.
In the June 2007 edition of Cosmopolitan, Simpson said that she hasn't lip synched since her Saturday Night Live incident, that she has "a little crush on Christian Slater", feels sexiest in bed, and that you can and can't have a good relationship without amazing sex.
Simpson was ranked as one of the "Hottest Women in Pop/R&B" by Blender in January 2007. She was later voted as number 16 in Maxim's 2007 Hot 100 list.
In June 2006, it was reported that Simpson seriously considered but later turned down a $4 million offer to pose nude for Playboy.
In early September 2006, Us Weekly reported that Simpson and Braxton Olita had split up. Simpson's rep said that the couple "broke up about a week ago. They have decided to take a break."
Eventually the two began to acknowledge the relationship. In mid-2007 Wentz spoke about their relationship to InTouch magazine, saying of Simpson that "I have never met somebody who makes me feel the way she makes me feel", although he denied rumors of engagement.Simpson has since discussed their relationship in a number of magazine interviews, including the September 2007 issue of Seventeen magazine and the December 2007/January 2008 issue of CosmoGIRL!. In March 2008, Simpson and Wentz presented the award for Favorite Reality Show at the 2008 Kids' Choice Awards.
The couple announced that they were engaged on April 9, 2008. Simpson had previously been wearing what she described as a "promise ring" from Wentz for several months. On April 14, Us Weekly and OK! magazine reported that Simpson is pregnant. Wentz promptly denied this in an e-mail to MTV News, although Simpson, in an interview the next day, chose not to confirm or deny the report, saying that it was something to "keep personal", and on TRL she noted that rumors claiming she was pregnant had been appearing for so long that, if they were all true, she "would have had a baby by now". Due to the marriage, Ashlee has legally changed her name from Simpson to Wentz with her stage name changing to "Wentz". Simpson says:
"I think that that's something that a woman should do when they're marrying a man. It's a tradition that I think is a great tradition."
On May 28, 2008, Simpson and Pete Wentz announced on Fall Out Boy's official website that they are expecting their first child. "While many have speculated about this, we wanted to wait until the press was gone to have our first child. This is truly the most joyous time in our lives and we are excited to share the happy news and start our family." On November 20, 2008, Simpson gave birth to their son, Bronx Mowgli Wentz.