The blonde beauty, younger sister of supermodel Jessica Hart, accepted Palmer's proposal during a vacation in the south of France last week, reported Daily Mirror.
Hart revealed her partner popped the question on the beach after they swam out to a private cove.
"He asked me to stand and got down on one knee, pulled out a gorgeous little ring that looked like the sunshine, a yellow diamond on a... Gold band... 'Can we jump in the water I asked?' Needing to make this moment feel real... We splashed and kissed, did somersaults and I yelled at the top of my lungs, 'Yes'," Hart said.