Matoka and his friend Daniel Leota came into the nightclub and the latter was acting aggressively, she said.
"When he first walked in, he wasn't looking at us but he was shouting. He turned round and saw us. He saw George and asked for a 'one out'," she said, through tears.
When the brawl erupted, she said she grabbed the rugby player and tried to pull him away from the melee.
It is alleged a brawl started because of tensions between Tongans and Samoans.
Crown prosecutor Josh Shaw told the jury, after the initial fight had subsided, George Moala then attacked Mr Matoka as he was being helped downstairs by bouncers.
Ms Fosita said the man threw a punch which clipped her lip, before her boyfriend stepped in and punched him back.
She could not remember seeing Siua Moala do anything that night, she said.
Mr Shaw suggested she was "choosing not to remember" and doing so because she did not want to get her boyfriend in trouble.
The trial, before Judge Rob Ronayne, is expected to finish tomorrow.