In the new screens released for Soul Calibur IV, Ivy can be seen with two pendulous globes dangling from her chest. They look like tumors.
If I were in charge of her character arc, here's how I'd plot it:
Ivy has entered the competition in order to fund her dangerous love of surgical modification. Her obsession with breast size has seen her go under the knife six times now, the increases leaving horrible stretch marks on her skin and layers of scar tissue beneath each breast. She plans to go bigger next time, despite warnings from her doctor. If she can win the tournament, she'll have enough cash to fly to Eastern Europe where a doc exists who will do the surgery regardless of the risk.
If you win as Ivy, the final cutscene shows a series of snapshots of her in a skimpy bikini, breasts swollen to even more gigantic proportions, smile plastered on her face. It fades into a dimly-lit room, Ivy on a surgical table, a doctor smeared with blood, his forehead covered in sweat. The heart monitor flatlines, the doctor works furiously for a minute, the nurse handing him gauze and sutures, but to no avail.
Close-up of Ivy's blank eyes as the announcer says, "Ivy has been defeated, but the soul still burns."