"I needed to forget what people were saying about me," said the 30-year-old who broke down in tears after crossing the line to win in a time of 33 minutes and six seconds (33:06) at Kingsmead.
The Soweto-based runner tested positive for the banned stimulant methylhexaneamine in 2011, for which she received a back-dated one-year suspension in January 2013.
It was a lesser punishment in exchange for evidence she gave against coach Livingstone Jabanga who gave her tablets containing the stimulant before a 10km race in August 2011.
Zimbabwean Rutendo Nyahora took second place in Durban (33:41) and Rene Kalmer dipped under 34 minutes to claim third in a time of 33:49 in the third leg of the Grand Prix series.
Phalula, who has an 18-month-old child, said she did not anticipate any future doping problems.
"I had to make a comeback for myself and my baby, for my sister and my family and for everything I've been through.
"I know that I'm clean this year - I'm running clean and proud. I don't want anything that will connect me with a banned stimulant."
Athletes were randomly tested for doping while on Sunday no tests were carried out after the event.
Since the doping allegations were first levelled against Phalula, she maintained the infringement lay with Jabanga's actions.
"Through the years, it's been a struggle with the doping thing I was caught in.
"That gave me a bad name, testing positive for something in my body which was something I didn't expect. The guy came to me and gave me the banned stimulant which was very bad for me. I didn't give up, I told myself to not give up and believe in myself."