Walder is best known for her recurring roles on Gilmore Girls as Janet Billings, How I Met Your Mother as Shannon, and Mad Men as Sherry. She has appeared in over 40 television shows, including New Girl, Franklin & Bash, Fairly Legal, The Good Wife, Supernatural and Rules of Engagement. In 2007 she played Trevor Wright's girlfriend in the award-winning independent film Shelter. In 2014 she starred in the horror film Come Back to Me.