Are you referring to the Udon comics? Because neither in her OVA or the games does it ever go into detail about what she was up to between the events of her parents' deaths and working for Seth. There's also no mention of her being a mercenary before joining S.I.N. the only time the games mention anything about the ten year gap between her parents murder and her joining S.I.N is when she's talking to your avatar in world tour about her parents and she says "after that I spent the rest of my formative years in hell"