Mary Claire Cheney is the second daughter of Dick Cheney, the former Vice President of the United States, and his wife, Lynne Cheney. She is openly lesbian, has voiced support for same-sex marriage, and has been credited with encouraging her father to support same-sex marriage. Wikipedia*
On the C-SPAN Networks:
Mary Cheney has one video in the C-SPAN Video Library; the first appearance was a 2006 Interview.