Once part of Hondo Ohnaka's band of Weequay Pirates (though not a Weeguay herself) Julia found herself bathing in expensive spices and riches, until one day she was fraud for mutiny and to be executed by Hondo himself.
Hondo, though, saw through the lies and helped her escape. He wanted to clear charges but there was no evidence that could settle the entire conflict. Hondo told Julia to go to Yavin 4. He didn't say why.
She left for Yavin 4 and several days later found the Rebel Alliance and enjoyed they're comfort and decided to stay and fight the Empire.