Wasilewski's first role came in the 1994 Japanese animated film Heisei tanuki gassen pompoko, where she was one of the additional voices dubbing in English. She is also known for her television roles. She studied acting at the Catholic University in Washington, DC and early on performed in musical comedies at area dinner theaters.
She has made guest appearances in TV series, such as Friends, Two and a Half Men, George & Leo, Total Security, Saved by the Bell, Party of Five, Diagnosis Murder, State of Grace, The Nightmare Room, Providence, Charmed, Cold Case, ER, General Hospital, Push, The West Wing, Wonderfalls, The Bernie Mac Show, Boston Legal, Family Guy, Monk, MAD, and many more.
She voiced Misty and Tuck on the Nickelodeon animated series My Life as a Teenage Robot in 2003, and also voiced Laura in Scooby-Doo and the Alien Invaders. She voices a veterinarian named Dr. Glove in Back at the Barnyard. In 2007, she voiced Garfield's love interest Arlene in the animated direct-to-video film Garfield Gets Real, and reprised the character on The Garfield Show, the following year. She is also the voice of Bessie in Random! Cartoons and she also voiced Terk in a Tarzan video game. She is voicing Ortensia, Oswald the Lucky Rabbit's cat girlfriend in Epic Mickey 2: The Power of Two.
Most recently in the 2010 feature film RED, Wasilewski appeared in a cameo alongside Bruce Willis and John Malkovich in which she played a doomed "gun for hire" sent to assassinate them, her character had a swift exit after calling Marvin Boggs an "old man".