Finnessey was born to Patrick and Linda Finnessey, and she grew up in Florissant, Missouri. She attended McCluer North High School public high school for two years where, according to an interview with ABILITY Magazine, she was teased a lot for her appearance. Finnessey recounted that she “had a mullet, tinted glasses, acne and braces.” The teasing made it difficult for her to focus on her studies, so for her junior year she transferred to the private all-girls Incarnate Word Academy, where she graduated in 1996. She completed a Bachelor of Science degree in psychology from Lindenwood University in December 1999. Following graduation, she worked briefly as a full-time substitute teacher in Jackson, Missouri, before starting graduate school. She began working on her Masters in Counseling, also at Lindenwood, but postponed her studies after being crowned Miss USA in 2004.

Finnessey first competed in the Miss Missouri USA 2000 pageant in 1999 where, as Miss Saint Louis County in her senior year of college, she finished first runner-up to Denette Roderick. She competed again in the following year (2000) and placed second runner-up behind first runner-up Melana Scantlin and winner Larissa Meek in the Miss Missouri USA 2001 event.

In 2000, Finnessey competed in the Miss Oktoberfest pageant and was third runner-up. The pageant was won by Jenna Edwards, who had previously been 1999 Miss Teen All-American and would later hold the Miss Florida 2004 and Miss Florida USA 2007 titles. First runner-up was Jennifer Glover, the previous Miss United States International 1999 and the future Miss California 2002 and Miss California USA 2001.

On November 18, 2000, Finnessey won the Miss Jackson title in the Miss Missouri system and finished second runner-up to Jennifer Hover in the June 3–9, 2001 Miss Missouri pageant held in Mexico, MO. Finnessey won the Miss St. Louis Metro local title in the Miss Missouri system and went on to win the 2002 Miss Missouri title, succeeding Hover. She won the contest despite having slammed her hand in a car door that weekend. During the contest, she performed an arrangement of “Flight of the Bumblebee” on the piano for her talent. During her on-stage interview as one of the five finalists, she was asked what she learned having three brothers and she answered to be quick in the bathroom.

Finnessey authored an award-winning children’s book. Her book, which was published on August 1, 2002, was entitled Furrtails and helps the effort to integrate intellectually disabled children into regular classrooms and helps children appreciate individuality and understand their peers who have disabilities. She was recognized with an Authors Who Make a Difference award, known as AWMAD, (from Infinity Publishing) and a Ryan Brems Award for this work. She authored a second book entitled Suzanna the Banana.

As Miss USA, Finnessey went on to represent the United States at the international Miss Universe competition held in Quito, Ecuador, in May 2004, culminating on June 1, 2004. She placed first runner-up in the internationally broadcast competition, behind winner Jennifer Hawkins of Australia. The event was hosted by Bush and Daisy Fuentes and the judges included Petra Nemcova, Emilio Estefan and Bo Derek.

According to the press release issued at the time of her first public appearance as Miss USA on April 17, 2004 in New York City, she plays both the violin and piano. She also practices yoga, meditation and performs knitting and abstract painting. In 2003, she dated August Busch IV and has also dated Italo Zanzi. She is a Republican, and during her Miss USA reign, she attended the Commander-in-Chief’s Ball at the Second inauguration of George W. Bush.

Finnessey provided color commentary at the Miss USA 2005 pageant live from Baltimore, Maryland, on April 11, where she was the outgoing titleholder. On July 23, 2006, she also co-hosted the Miss Universe 2006 pageant live from Los Angeles, California, as a commentator with Carson Kressley. The show’s main hosts were Carlos Ponce and Nancy O’Dell. Finnessey has also co-hosted subsequent Miss Missouri USA pageants. She again served as a commentator for the Miss Universe 2011 pageant in São Paulo, Brazil along with Jeannie Mai on September 12, 2011.

She also has appeared in several documentaries produced by GSN. She has also appeared on the NBC reality show The Apprentice (February 15, 2005, episode 3.5), in the November 13, 2004, 20 Sexiest Men and 20 Sexiest Women specials on CMT, and as Grand Marshal in the November 25, 2004, Macy’s Thanksgiving Day Parade. She was named one of the Ten Outstanding Young Americans of 2006 by the Jaycees. She also appeared alongside Chris Myers as part of the coverage of the New Year’s Eve 2007 Festivities for Fox. On March 19, 2007, Finnessey debuted on the fourth season of Dancing with the Stars. Her professional dance partner was Brian Fortuna, and she was the second celebrity voted off the show. On October 31 and November 21, 2007, she appeared as a guest celebrity on NBC’s Phenomenon. She also hosted Hollywood Fast Track, a web based show about movies, music, and trends in Hollywood. She is also the host/co-host of several TV Guide Network specials. On September 2, 2008, Finnessey was on the season finale of Wanna Bet? on ABC, where she made a record for the biggest successful bet on the show betting $20,000 in the 1st best. Finnessey lost in the end betting $40,000 and guessing incorrectly. In August, 2010, she appeared on a special “Girls of Summer” week airing of NBC’s Minute to Win It on an episode called “Last Beauty Standing.” The episode featured 10 beauty pageant winners competing for $100,000 towards their chosen charities along with a chance to win a $1,000,000 challenge. At the Miss USA 2011 competition, she was among the 31 former winners who were part of a photoshoot layout for Time Magazine. She played the role of Stephie in the Roger Corman-produced Sharktopus (2010) which aired on the Syfy Channel three years before the same network made waves with its Sharknado movie franchise.

After completing her reign as Miss USA, Finnessey became a co-host of Lingo and PlayMania on GSN. She hosted Lingo from August 2005 at the start of the show’s fourth season until the show went on hiatus in 2008. In April 2006, she began her turn with the interactive series PlayMania, which broke into two shows on February 23, 2007. Finnessey became the co-host of the quiznation spinoff, a revised but similar version of the original PlayMania. She remained a co-host until October 21, 2007, several days before the show’s finale. She also was a sideline reporter for the CBS tournament blackjack series Ultimate Blackjack Tour.

She joined a panel of celebrity judges to judged Miss USA 2009 pageant held at the Planet Hollywood Resort & Casino, Las Vegas, Nevada on April 19, 2009. That year when Miss California USA 2009 Carrie Prejean caused a notable controversy during her on-stage finalist interview with a response that she was opposed to same-sex marriage, Finnessey participated in a Miss California USA organization public service announcement promoting diversity along with several other Miss Universe Organization beauty pageant titlists.

In January 2012, she became one of the original reporters for ENTV News (a branch of TVLine) on a premium YouTube Channel. In March 2013, she was selected as one of 36 bachelorettes to compete on the reality television show Ready For Love. Finnessey was the winner for bachelor Ernesto Arguello, but the relationship ended briefly after the show.

On August 8, 2013, she was named as one of five correspondents for the entertainment magazine, OK!TV, that was scheduled to debut on September 9.

In 2013, Finnessey became a contestant on Ready for Love where she competed for the attention of Ernesto Arguello. She won Arguello’s heart on the show, but the relationship was short-lived in real life. Later that year, she posed nude for a PETA anti-fur campaign opposing the distribution of fur coats as prizes during beauty pageants. On September 24, 2014, Finnessey announced on Twitter that she became engaged to businessman Ben Higgins. They were married on July 11, 2015, according to another autobiographical tweet. The couple has three sons; Finn Arthur (born June 10, 2016), Bodhi James (born May 1, 2018) and Charlie Bear (born May 5, 2020).