I get the feeling if it was a simple "big scar", she wouldn't be as concerned about exposing it. I'm not saying she'd suddenly be running around half naked like a lot of RPG females, I just mean her coming out and saying to Arnaud "I have a large, ugly scar!" wouldn't be as hard. I seem to recall her having problems coming out and saying the whole "My body is basically mutilated beyond reason from an accident, and looking at it would scar you for life!"
I also would find it hard to believe she has those occassional health problems from a simple scar, but...maybe I'm over analyzing here.