Dr Kristi Funk treated the Oscar-winning actress and mother-of-six, who opted to have surgery after discovering that she carried a faulty gene which put her at high risk of developing cancer.
Dr Funk said Angelina "waited to find the perfect timing in her personal and professional life, but I think most importantly in her soul," to speak about her decision.
"She is intensely private, but she calculated the moment when she would be ready to reveal something so personal," she added.
"When someone who is arguably the most beautiful woman in the world removes the part of her body that is symbolic of femininity and sexuality, you have to say, 'Why would she do that?'," said Dr Funk in an interview with Los Angeles magazine.
Knowing the impact that the news could have and awareness she could raise, Brad Pitt's fiancée was not able to keep the decision to herself, her surgeon said.
"She knew always that in her philanthropic core she couldn't keep this a secret and be who she is," Dr Funk explained. "She always knew."
Angelina courageously revealed the news of her double mastectomy in a powerful article for the New York Times.
After the news broke, scores of women showed their support for Angelina and praised her brave move.
"I have a lot of respect for Angelina Jolie. Tough decision and brave to go public with it," tweeted Dawn O'Porter, while actress Kristen Bell called her article 'admirable'.
"I commend Angelina Jolie for her courage and thoughtfulness in sharing her story today regarding her mastectomy. So brave!" wrote Sheryl Crow, who has also suffered from breast cancer.
The American actress made the difficult decision to have a double mastectomy because she carried the "faulty" BRCA1 gene which means she was much more likely to suffer from breast or ovarian cancer.
The Mr and Mrs Smith actress underwent the three-month medical procedure, which involves tissue being removed from both breasts, in April.
Angelina's mother, Marcheline Bertrand, died of ovarian cancer, which is also associated with the gene, in 2007. Her aunt Debbie Martin passed away from breast cancer shortly after Angelina revealed the news.