Mary Cheney has decided to wade into Indiana's fight over whether to adopt a constitutional ban on same-sex marriage, hosting a reception in Indianapolis on Dec. 11 to raise money for opponents of the amendment.

The move comes as her sister Liz Cheney's position on gay marriage and the family's internal feuding over it hang over Liz Cheney's 2014 Senate campaign.

Mary Cheney, who is lesbian and married with two children, has publicly clashed with her sister over the issue of gay marriage in recent weeks. Liz Cheney is running in a primary against Sen. Mike Enzi (R-Wyo.) and has declared she opposes same-sex marriage.

In an e-mail to backers of the group Freedom Indiana, Mary Cheney -- a Virginia resident -- wrote that she felt compelled to fight the constitutional amendment in Indiana out of concern for same-sex couples and their children in the Hoosier State.

"There’s nothing I wouldn't do to protect my wife Heather and our two children," she wrote. "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."

The legislation first passed in 2011. It must again earn the approval of the state legislature early next year and then would be on the ballot in 2014.

Mary Cheney and her wife, Heather Poe, recently targeted Liz Cheney's position on gay marriage, suggesting her personal actions toward the two of them suggest she is accepting of their union.

Former vice president Dick Cheney and wife Lynne -- parents to both Liz and Mary Cheney -- appeared to side with Liz Cheney, saying her position on marriage has been consistent, despite being respectful of her sister.

Here's the entire e-mail from Mary Cheney:

Freedom means freedom for everyone.

For me, that’s not just another saying. It’s who I am -- the core of what I believe. No one should be denied the fundamental liberties we all deserve.

That’s why when I heard about HJR-6 -- the proposed constitutional amendment that would permanently ban all protections for same-sex couples and their families -- I knew I had to join the powerful bipartisan movement that’s working to stop this anti-freedom amendment.

On Wednesday, December 11th, I’m hosting a reception in Indianapolis to support Freedom Indiana’s crucial efforts to defeat HJR-6 -- and I hope you can join us.

Click here to get your ticket now.

Speaking out against HJR-6 isn’t a matter of politics. It’s about family. It’s about everyone feeling welcome in the state they call home.

Freedom Indiana’s campaign is strong. 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.

Join me in Indianapolis on Wednesday, December 11th as we raise crucial funds and resources to protect Indiana’s constitution. Click here to get your ticket now.

Thanks for everything you're doing to stop HJR-6.

See you soon,

Mary Cheney