Ms Elder was a good employee, Mr Barnett said. "She's been here the last few years, as you know, but she's doing some time with her dad at the moment."
Sir Paul, who was invested as a knight at a special ceremony at his home in Hawkes Bay this week, said his daughter had turned a corner since her drug problems.
"(She's) looking resplendent and beautiful, in the mindset of a vibrant new life, in a new direction, knowing her direction and determined to do it too," he said.
"She won't say so, but Millie is wonderful. The Governor-General told me that one of my revealing features was standing up for my daughter when she got in trouble. I had no trouble doing that because she's family. When kids get into trouble, you've got to help."
According to one source, Ms Elder has taken an interest in makeup artistry and may be looking to leave the chamber to study the craft.
Ms Elder, who declined to talk publicly, struggled with drug use in the past, appearing in court several times for possession of P.
At the time, Sir Paul appeared in the media and in court, vowing to support her and leading a fight against the drug.
"We love Millie very much, and the whole family - the whole family - is working together to offer her our support ... Millie is a girl with a good heart," he said in 2007.
A year later, he spoke again, at her sentencing, asking the court to show compassion for his daughter and not allow a conviction to wreck future career and overseas travel plans.
"We're so proud of her. She's made such progress," he said.
Ms Elder has said she quit the drug in 2009.
