Dingfelder was appointed to the Oregon House of Representatives, representing District 19, in April 2001, to fill a vacancy created by the resignation of Jo Ann Hardesty (née Bowman).[2] After redistricting based on data from the 2000 Census, Dingfelder represented House District 45. In the 2007–2008 session, Dingfelder chaired the House Energy and Environment Committee, and sat on the Agriculture and Natural Resources Committee.[3] She also chaired a conference committee.[4]
In 2009, she joined the Oregon State Senate representing District 23 (Northeast and Southeast Portland). In the Senate she chaired the Senate Environment & Natural Resources Committee, and sat on the Joint Ways and Means Subcommittee on Natural Resources and the Senate Judiciary Committee.[5] Her support and advocacy in animal-related measures saw her labeled as a 2011 "Top Dog" by the Oregon Humane Society.[6] In October 2013, Dingfelder resigned from the Senate to join the staff of the mayor of Portland.[7] She resigned in July 2015 to pursue other interests.[8]