"I'll feed Belle as long as she asks," the mum-of-two insisted. "I don't know how long that will be. It will be the same with my son Beau. I don't think there's anything weird about it."
Belle, who is in Year Two at school, asks to be nursed whenever she's "tired, ill or simply wants some bonding time" with her mum. That means Denise breastfeeds her daughter as often as twice a day to as little as once a week. She also breastfeeds her 18-month-old son Beau.
Denise claims Belle rarely gets sick, is at the top of her class, and is a talented musician.
"I have two healthy, bright, confident children who I truly believe have benefited from breast milk, and continue to do so," the 44-year-old says. "There are things I get out of it - like calm, happy children. But I can say with certainty I've done this entirely for the benefit of my kids."
Denise has got used to comments about her decision to breastfeed for so long. "I used to get the odd comment from relatives who'd say 'here we go with the milk thing again'," she said. "But I think because people know I'm confident in my decision they let me get on with it."
Interestingly, when Sumpter had Belle she only expected to breastfeed for six months to a year, but changed her mind when she saw how much her little girl needed her milk. The proud mum said: "If you'd asked me five years ago I never would have thought I'd still be breastfeeding Belle. However, it turned out to be one of the best things I could have done for my family."
What do you think? Could she just give her daughter a cuddle or is there nutritional benefit to breastfeeding a six-year-old?
More on Parentdish: Why I still breastfeed my four-year-old