Thomae, 20, first met Jackson, 43, when she was 13, London's Sun reported Monday.
"I really cared for him. He cared for me. We kiss each other. The rest is private," Thomae, 20, told "ET" as reported in the Sun.
Asked if she would marry the pop singer if he proposed, Thomae said "Yes. I'd say yes."
Thomae said she stayed at Jackson's Neverland Ranch, but never shared a bed with him.
"I stayed but we looked at movies," she said.
Thomae said she was at Neverland the same time as the young cancer patient at the center of Jackson's current child molestation charges.
Thomae said nothing happened between Jackson and the boy and Jackson treated the boy "like a brother."