Rylai's Crystal Scepter Cooldown?

Just finished a match. The opposing team had a Cassiopeia within their ranks. She rushed Rylai's first item, and began the steamroll of what would be a definitive defeat. There was no possible way for our team to reach her, as each time we were hit with her poison the Rylai's would proc and we would be slowed by 40%. Her Fangs being on such a low cool-down and her kiting mechanics enabled her to slow me, indefinitely. I suggest either a nerf to the cool-down of her Fangs, or adding a 3 second cool-down on Rylai's similar to that of Sheen. There is no counter-play to that level of ability. Being slowed without being able to hit her is maddening. Constructive criticism without aggressive behavior is welcome.