Born in Boston and raised in Newport, Rhode Island and Amherst, Massachusetts, Koslow wanted to be an actor even as a young age. After graduating with a theatre degree specializing in costume design from Virginia State University, Koslow signed on with a summer stock theater group in Virginia as a costume designer. She was also asked to audition for the role of Vera in the play Ten Little Indians. Koslow soon put her costume designing talent aside to become a full-time actress. While in an acting class, Koslow met a producer from The Young and the Restless who encouraged her to audition for his series. Koslow not only won the role, but found her husband, make-up artist Nick Schillace, on the show. Koslow was then cast as fashion designer Margo Lynley on The Bold and the Beautiful. Following this role, Koslow was cast as Kate Roberts on Days of our Lives.