Alexander began working in the adult industry as a stripper in Sacramento when she was 18, to supplement her daytime earnings as a receptionist. She appeared in several adult magazines with her first photo shoot being with Earl Miller. She started performing in adult films in 2001 beginning with a girl-girl scene in Hot Showers Number 2 and becoming a contract girl for Sin City in that year. In addition to a catalog of solely girl-girl hardcore work, she appeared in a handful of softcore erotic films produced by HBO and Cinemax such as Hotel Erotica, The Sex Spa, Sex House, and Voyeur: Inside Out. She also became a solo and girl-girl internet nude model. Alexander appeared in a mainstream film titled Spider's Web with Stephen Baldwin and Kari Wührer in 2002. Alexander has also done foot-fetish videos for FM Concepts.

Alexander was a contract girl for Vivid Entertainment from 2004 to 2009. After years of appearing only in girl-girl scenes, she began appearing in boy-girl scenes in 2005, including an interactive DVD and a feature role with Rocco Siffredi in Vivid's Lexie and Monique Love Rocco.

Monique makes a cameo appearance in the Season 3 finale of the HBO series Entourage. In 2007 she became a sports reporter on National Lampoon Comedy Radio's The Phil Show.

She was invited to Fox News show, Red Eye w/ Greg Gutfeld, to discuss a recent nonpartisan study that finds abstinence-only programs for teens do not work, whereas safe sex education programming is highly successful. Alexander discusses what being a Vivid Girl means to her as well as her preference for hands-on sex education, which aired on November 10, 2007. On February 15, 2008, she and Ron Jeremy represented the industry in a debate at Yale University against pornography opponents Craig Gross and Donnie Pauling.