Keena was born May 28, 1979 in New Jersey, the daughter of Mary, a nurse, and William Keena, Financial Sales Manager. She was raised in Brooklyn and appointed an older sister Samantha. During their childhood and once again at the end of high school, Monica visited Saint Ann's School, a private school advances in Brooklyn Heights. Monica said the inclusion in the LaGuardia High School of Performing Arts at the age of thirteen. Although the drama that it has chosen the department of their preference, it was dramatic in the vowels and departments of art. Shortly after take-off from their classes in Laguardia, Keena played in his first role in a film entitled Burning Love. Keena has continued to Bertha portrait of nature at a stage of reading Strindberg's father with Al Pacino, and took his first lead role of Snow White Sigourney Weaver against the wicked queen in the folktale-inspired Snow White: A Tale of Terror. It has, in many films and television projects, including the First TBS Original Movie daughter and debt and atonement Suburbia appeared in the Sundance Film Festival 2000.

Monica appeared in the film While You Were Sleeping with Sandra Bullock, The Simian Line, with Harry Connick Jr. and Lynn Redgrave and girls bathroom top of the valley with Julie Benz and Jonathan Brandis, in his last film role before his death in 2003 and the film was finally released on DVD just in 2005. In 2003, she plays the heroine, Lori Campbell, M. Freddy vs. Jason. In 2006, she played in the film Celia left in the dark. Keena had a recurring role as Abby Morgan Dawson's Creek and a leading role in the role of short-lived as a student unregistered Rachel. Monica also invited roles in series like Law & Order, Law & Order: Criminal Intent, Homicide: Life on the Street, Feds and Entourage. On the results page Medical ABC drama Grey's Anatomy, Monica appeared in an episode of the second season, entitled "Into You Like A Train" in which she played Bonnie, a patient was seriously injured in a massive accident. Monica later in the third episode of the season "Some Kind of Miracle", reprising their roles as Bonnie.