The flare-ups are treatable, but the virus stays in your body for life, there's no curative medication against herpesviruses. It won't kill you 99% of the time. It can cause encephalitis, some other serious conditions like trigeminal neuralgia and may contribute to Alzheimer's (still under investigation), but it doesn't reduce life expectancy or cause debilitating illness in the vast majority of carriers.
I think what the description of her behaviour is getting at is that it doesn't matter, deep down, what the facts of the matter are. If she cannot live with her body after it got infected, what's the point in living? More deeply, it's an issue of "what can be said to be an illegitimate reason to choose suicide". In a chapter of We shall now begin Ethics, Takayanagi remarks that people kill themselves out of boredom.
Of course, with a mindset like that, how would she have reacted had she known most people carry several viruses in their body, all transmissible, none treatable, some contracted from our mothers during birth or breastfeeding, and some of which can and do cause illness given the right circumstances?