Mary Cheney, the openly gay daughter of former vice president Dick Cheney, has joined the fight against a proposed constitutional amendment in Indiana which seeks to prohibit the state from recognizing any union other than a heterosexual marriage.

Cheney will appear at a December 11 event in Indianapolis to help raise money for Freedom Indiana, the group working to derail the amendment.

“There's nothing I wouldn't do to protect my wife Heather [Poe] and our two children,” Cheney said in an email to supporters. “And then I think about the thousands of same-sex couples and their families in Indiana who would be directly impacted by HJR-6, I'm committed to standing together and working across party lines to keep this amendment out of Indiana's constitution.”

House Joint Resolution 6 (HJR-6) sailed through the Republican-controlled General Assembly in 2011. A second voted needed before it can go to voters is expected to take place early next year.

“Freedom Indiana's campaign is strong,” Cheney wrote. “And as the start of the legislative session quickly approaches, we can make it even stronger by pitching in to support the grassroots work across the state.”

Cheney's participation comes after a public feud on the subject with her sister Liz Cheney, an opponent of marriage equality and a Republican candidate for the U.S. Senate.

(Related: Mary Cheney “not supporting Liz Cheney's candidacy.”)