Nicolet was born Danielle Diggs in Ashtabula, Ohio. Nicolet began acting in the early 1990s, appearing in a recurring role on the ABC sitcom Family Matters. In 1996, she landed the role of Caryn on the NBC sitcom 3rd Rock from the Sun, a role she would reprise through 2001. In 2005, Nicolet starred in the short-lived UPN sitcom Second Time Around. Entertainment Weekly named her the network's "breakout star." in review. After the series was canceled, she co-starred on the TNT medical drama, Heartland. That following year, Nicolet had regular role in the USA Network comedy-drama, The Starter Wife starring Debra Messing, the series also was canceled after one season. Nicolet has also guest starred on episodes of Stargate SG-1, Angel, The Bernie Mac Show, All of Us, CSI: Crime Scene Investigation, and Warehouse 13.

Nicolet appeared in various films including a small role as Samuel L. Jackson's character's teenage daughter in Loaded Weapon 1 (1990). She later had roles in Melting Pot (1998), opposite Paul Rodriguez and A Wonderful Night in Split (2004). In 2009, Nicolet starred opposite Cuba Gooding, Jr. in the thriller Ticking Clock (2009). In 2011, she co-starred in the Syfy original film, Red Faction: Origins, based on the video game. She also voiced Shaundi in Saints Row: The Third and continued to voice her in Saints Row IV and Saints Row: Gat out of Hell. In 2013, she starred in the short-lived ABC comedy series, Family Tools. She later had the recurring role on the BET comedy series, The Game, and guest starred on Elementary and The Flash.

In 2015, Nicolet was cast in the leading role in the TV One first original comedy-drama series, Born Again Virgin. She also was cast as female lead opposite Kevin Hart and Dwayne Johnson in the action comedy film, Central Intelligence directed by Rawson Marshall Thurber.