Sarah, 21, fulfilled that promise on Saturday, raising more than $3000 with a community walkathon.

About 50 people participated in Wollongong Walking Aid, organised with the help of University of Wollongong Rotaract Club.

Sarah told Keys about her goal when she won a competition to meet the star in December.

"She high-fived me and thought it was very good. She was really encouraging," Sarah said.

The charity provides antiretroviral therapies, life-saving treatment and support programs for children and families affected by HIV/AIDS in countries such as South Africa, Uganda and India.

"Keep a Child Alive triggered in me a greater sense of global awareness and a need for action to help those suffering unnecessarily in the developing world at the hands of greed, war, globalisation and corrupt leaderships," Sarah said.

"Fifteen million children (are orphaned because of HIV/AIDS) ... that have to look after themselves and try to survive. It just doesn't seem fair.

"I thought I would do what I could and a community walk was the first thing that came to mind that seemed profitable."

Sarah hopes to hold another event to raise money for a rape crisis centre and intends to volunteer with the organisation in Africa next year.