All her life, Mary had been the rose in her family of boys.
Even though she grew up with three brothers, she enjoyed doing the things any girl did - hanging out with her BFFs, shopping for dresses and collecting cute figurines.
Sure, she started out being a bit of a tomboy, preferring pants instead of skirts, and comic books instead of dolls, but which girl wouldn't growing up with three boys?
But when Mary turned 13, she found it strange that she did not have her period - like the other girls in her class. She has never had her period.
It was only earlier this year that Mary, 24, found out why - she was actually male.
The svelte 1.8m-tall lab technician from Malaysia got the news from a doctor here.
"I was shocked. My parents were equally shocked," Mary tells The New Paper on Sunday in an interview over Skype.
"It took me quite a while to piece together what the doctor had told me."
We are not using Mary's real name at her request. She does not want her friends and extended family to know about her situation.
Mary suffers from a rare condition called Androgen Insensitivity Syndrome (AIS), where a person is genetically male, but is resistant to male hormones. As a result, the person has some or all of the physical traits of a woman.
Mary said that after getting the shocking news, she was in emotional turmoil for a week.
By all accounts, Mary bears no man-like traits.
She was born a girl and brought up as one, even though she admits to being "a bit of a tomboy growing up", she says.
She adds: "But that was attributed to the fact I have brothers and was hanging out with them."
Mary's brothers are aged 19, 20 and 29.
She says: "Growing up, I love reading comics, especially the ones that have violence in them.
"I've always thought this was due to my brothers' influence. I never thought it was because of me."
She said there were clues about her condition when she was a teenager - such as the lack of menstruation - but she didn't think anything of it at the time.
"I did not get my period when I turned 13, but I wasn't anxious. I was told some girls get theirs much later." When she was 17, with no sign of her period her parents took her to a doctor in Malaysia.
"I was given medication, hormone pills I think, but there was no result," she says.