Aniston, 45, who has been engaged to Theroux for two years, said she is not a diamond girl and might not have picked it for herself, reported the New York Post.
"It's a rock, I know. He rocked it up. It took me a while to get used to it. I'm not a diamond girl. I'm more Indian jewelry and stuff," she said.
Aniston said she considers Theroux a blessing sent to her by her first love, who died of a brain tumour when they were young.