it's not just the curse. to her, caring about others, desiring their company, falling in love, etc are the insanity of the privileged who can afford to care about something other than mere survival. if she kissed sherbet and, more importantly, wanted it and liked it, it would reveal the lie of her worldview. she'd have to confront that not only does she care for sherbet, she's probably cared for many people in the past, but, to avoid getting hurt, she's quashed those feelings and treated them as tools instead. and that would hurt.
of course she can't kiss sherbet. she'd have to believe herself capable of love to do so. and, even tho she clearly is capable, she cannot believe it.