"We had been together for two years when I went public and he had no idea."
Barnard, from Minneapolis, does not want other young girls to have to go through what she did.
"At the time I would rather have not been alive than have lymphoedema. After opening up, I feel so much happier.
"I was extremely depressed I would come home from school every day, cry and ask why me - it felt like my life was over at 15."
The condition began in puberty when her lymph nodes did not grow large enough to process fluid, which then remained trapped in her leg. The result was extreme and painful swelling in her right leg.
Now she has to wear compression pants for 70 minutes every day to provide temporary relief from the pain.
Despite the condition having no known cure, Barnard would be able to gain long-term relief from treatment with liposuction.
But health insurance companies consider her condition to be cosmetic and have denied her the treatment she needs.
The longer Barnard goes without the surgery the worse her condition will become so she has decided to pay for the procedure herself with the help of her friends and family.