Judge Bruno Tonioli told the former child star that he had "great showmanship" but needed to watch his "weird" hand.
Kirstie, who came second with Maksim Chmerkovskiy, gained a 23-points total after she was awarded an 8 and revealed she wants a 9 next time.
The 'Fat Actress' star said: "I did work hard, and I'm going to work harder now. I've had a taste of an eight, I want a nine."
The lowest score of the night went to talk show host Wendy Williams, who scored just 14.
Commenting on her dance, head judge Len Goodman said: "You need to unleash the beast. I thought, 'Here we go, loud and proud - you got your dumplings boiling over.' But it was quiet. It was timid."