Like Mitt Romney, she was raised as a child of Republican privilege. Unlike MR, she derived different lessons from that world. Two quotes from the Minutaglio and Smith bio I've been reading:
[Sara] Speights says, "Molly was incredibly disciplined. I think she was dead determined not to act nouveau riche. She didn't want to be one of those people. She wanted to be a genuinely gracious Southern lady. She made a conscious decision on how she would treat people and she lived by it. People would always come up to us in airports and she was always nice to people." [emphasis mine]
-- Minutaglio, Bill; Smith, W. Michael (2009-10-15). Molly Ivins: A Rebel Life (Kindle Locations 4426-4428). Perseus Books Group. Kindle Edition.
As he watched his sister, Andy thought that her success and generosity were almost easy to understand. She had grown up disliking the pecuniary people who lorded over others, and she was determined to move in the opposite direction.
-- Minutaglio, Bill; Smith, W. Michael (2009-10-15). Molly Ivins: A Rebel Life (Kindle Locations 4458-4459). Perseus Books Group. Kindle Edition.