Benz was born in Pittsburgh, Pennsylvania. Her father is a surgeon and her mother was a figure ice skater. Benz began ice skating when she was three, competing in the 1988 US Junior Championships with partner David Schilling, finishing in 13th place. When she was 14, she suffered a stress fracture in her leg causing her to take time off. Benz graduated from Franklin Regional High School.
At the age of 15, Benz was told by an acting coach that she would never make it as an actress. By 1989, her figure skating career had ended and she got involved with the local theater.
Her first small movie role was in "The Black Cat" segment of Dario Argento/George A. Romero horror film Two Evil Eyes. A year later, she was cast in TV show Honey, I'm Home which was cancelled after two seasons.
After graduating from high school, Benz enrolled in New York University to study acting. After graduating from there , she moved to Los Angeles where she was offered a bit part in a 1994 episode of Married...With Children. Her other TV roles included Boy Meets World, Diagnosis Murder and The Single Guy.
In 1996, Benz auditioned for the lead role for upcoming TV series, Buffy The Vampire Slayer but lost out to Sarah Michelle Gellar. However she was offered the small role of Darla, a vampire who had the first line in the show's run. She appeared in more TV roles including The Big Easy and Fame L.A. She made two movies, dark comedy Jawbreaker and Dirt Merchant. The first season of Roswell saw Benz play undercover FBI agent Kathleen Topolsky.
Benz reprised her role of Darla for TV series, Angel in 2000, appearing in at least one episode every season and appeared as Ursula in George of the Jungle 2. Benz appeared in Peacemakers, Coupling, NCIS and Oliver Beene. She landed the lead role of Annie Garrett in the Hallmark TV movie The Long Shot. Benz also provided the voice of Miranda Keyes for the video game Halo 2, though she did not return to the role in the sequel Halo 3 as Bungie wanted to try a new direction with the Miranda Keyes voice by giving the character an accent, replaced by Justis Bolding. She played the lead role of Danielle in Bad Girls From Valley High (a film shot in 2000 under the title A Fate Totally Worse Than Death) which was released on DVD in 2005. She had a small role in the critically acclaimed TV movie Lackawanna Blues. In the Sci-Fi Channel original film Locusts: The 8th Plague, she played the lead female role Vicky. She also appeared in the straight-to-DVD movie 8mm 2 as Lynn. The film was originally called The Velvet Side of Hell and was not supposed to be a sequel to 8MM. Benz appeared in episodes of Supernatural, CSI: Miami, Law & Order and CSI: Crime Scene Investigation. She had a supporting role in a Swedish independent movie called Kill Your Darlings, a lead role in the Lifetime movie Circle of Friends and joined the cast of TV show Dexter as Rita Bennett. Benz played a lead role in the fifth film of the popular horror franchise, Saw V, as Brit, a real-estate developer who is one of Jigsaw's five victims. She had a supporting role in Punisher: War Zone as Angela. Benz co-starred with Sylvester Stallone in 2008's Rambo, the fourth film of that series.
She plays the title role in the short film Kidnapping Caitlynn, written by her close friend Jenny Mollen, premiered at the Vail Film Festival 2009 and was released online April 6, 2009. She starred in the Lifetime movie Held Hostage as Michelle Estey in July. She also starred in the Hallmark Channel movie Uncorked as Johnny Prentiss which premiered in the UK in July 2009. She is the lead female character Special Agent Eunice Bloom in The Boondock Saints II: All Saints Day which had a limited release on October 30, 2009, and was released on DVD March 9, 2010. She has been cast in another indie film called Bedrooms as Anna. She plays Frankie in the upcoming movie Answers to Nothing which is scheduled for a 2011 release.
Benz appeared on The Soup with Joel McHale. Benz next took a recurring role on Desperate Housewives as Robin Gallagher, a stripper with a heart of gold and a Masters degree in education who gets offered the chance to transition into a more legitimate career. The character of Robin is further developed when the audience discovers she is a lesbian and begins an affair with housewife Katherine Mayfair (Dana Delany). After the Season 4 finale of Dexter, she returned for the Season 5 premiere.
In early 2010, ABC announced that Benz had landed a lead role as Stephanie Powell, in the network's drama pilot No Ordinary Family. Production of the series commenced the following May and it premiered on September 28, 2010, as part of the 2010–11 season. On May 13, 2011, No Ordinary Family was canceled after one season with only twenty episodes filmed. In 2011, she was cast in the new CBS TV show A Gifted Man. She was originally a co-star but was downgraded to recurring. A Gifted Man was canceled by CBS in May 2012 after one season of 16 episodes. She will also be starring in TV movie Ricochet as Elise Laird. Benz plays the lead female role, Mayor Amanda Rosewater, in the new science fiction series Defiance and also stars in the upcoming indie movie Supremacy and the unaired TV pilot Middle Ages.
Benz was married to actor John Kassir. They married in 1998 but filed for divorce in December of 2007. Benz re-married in 2012 to Rich Orosco.
- She often plays women who have suffered high traumas or distress
- Good friends with Buffy and Angel co-stars, Charisma Carpenter and Eliza Dushku, Buffy co-star Clare Kramer and Dexter co-star Jaime Murray.
- Auditioned for a role in Eyes Wide Shut but decided against it when she discovered there would be scenes filmed where she'd be topless.
- "I didn't expect them to write such a beautiful ending. I really think it was one of the most beautiful gifts I've ever received as an actor. The last three episodes of her life are so wonderful. They were such a gift to play. It was really amazing. They sent me the script and I was on lunch. I was in my trailer crying. Everybody was asking me if I was okay, and what was wrong, and I had to say it was nothing, and that I was fine. You don't want to tell anyone anything - and, of course, we're not allowed to tell anybody anything. I think she truly is one of the most amazing characters on television." - On her character Darla in Angel.
* "I loved the episodes where Rita dressed up as Lara Croft... and gave Dexter things. It was such a fun scene to play and it's the first time you really saw a little bit of her strength and her playfulness, and it was so nice to do after playing so much of this vulnerable, beaten-down woman, to have this fun moment with Dexter. I also love the scene towards the end where she confronts Paul [Rita's ex-husband] in prison and basically lays it on the line from a place of great strength, where she finally just tells him how it's going to be and how he needs to explain to the kids why he's in prison." - Her favorite scenes in Dexter.