Well Skye, Kathy's first professional job in entertainment was with THE Second City improv group in Toronto (where she also met her good friends Colin Mochrie and Ryan Stiles), it was a goal of her's when she was a child to be a part of Second City, and she was with them for five years, and even won two awards for a couple of shows she co-wrote and performed in. After that, she and two friends of her developed sort of a spin-off of Second City called Not to Be Repeated (which was later adapted into a short-lived sitcom on Canadian TV and renamed This Sitcom is... Not to Be Repeated) in which the three would take a line that the audience suggested, and use that as an episode title, then completely improvise an entire show on the spot. After that she's done a few other small improv gigs through-out Canada, and in fact in 2000 she was the very first to win the Canadian Comedy Award for Best Female Improviser (while that same year Colin Mochrie won for Best Male Improviser)!
So she's had quite an impressive background in improv prior to Whose Line?, and she's said that improv was always her greatest passion... but it's like once she did Whose Line? I haven't seen or heard of her doing any form of improv after that. Good thing is at least years later in an interview in Canada she dissed the Whose Line? producers. There's even a history behind how she got on the show in the first place, but I believe I've explained that before, and This Snowthy is Not to Be Repeated!