While she won't actively try to hide what her disease so clearly is to those that know of the Cold Death she won't go out of her way to note that she has such an illness. However, since fleeing from her home, she uses it, coupled with her identity as a princess, to hide the true scope of her past and what she was trained as when she needs to.
She guards her identity as an assassin closely for several reasons. The first is simply because she'd been raised to do so, yet that point is not as binding as it once would have been. The main reason now is to be underestimated and knowing that if she were to reveal her true talents it would only heighten her family's pursuit in an attempt to silence her before the secret of their dark organization is revealed to the world. It's a daggers edge, having the skills to be able to protect herself from most threats, and yet having to hide them. That coupled with her worsening condition over time also aids to her selectivity on when to actually use her training.