Is the Underground Man (Hedda Gabler) a pathological narcissist, or is his (her) perception of society and his (her) place within it rational?

Hedda is a narcissist, but at the same time, one could argue that she merely sees life more realistically and practically than others do. If her mindset is pathological, this is perhaps less due to any inherent mental disturbance than to the convergence of anomalous situations and eccentric characters Ibsen presents in his play.
Hedda is married to the rather nerdish Tesman, a man whose absent-minded and remote bearing would drive most women crazy, whether they are narcissists or not. The intrusion of her former lover Eilert Lovberg into her life becomes a trigger for Hedda's rebellion not only against her restrictive marriage, but against the whole set of rules by which women at that time were expected to live. She is, to an extent, arguably a more aggressive and defiant version of Nora in A Doll's House.
Hedda's antithesis is the self-effacing and submissive Thea, whose devotion to Eilert Lovberg is unrealistic and would be even slightly comical were it not pathetic. Though to nineteenth-century audiences, a woman like Thea might have seemed a paragon of virtue, Ibsen's intention, given his own liberal thinking, may have been to show her as a relic of traditionally servile womanhood. Hedda destroys Lovberg's manuscript not simply as a means of destroying the intellectual bond Lovberg has had with Thea, but in some sense to help her husband Tesman, since Lovberg is his rival. The attempt by Tesman, absurdly, and by Thea together to re-create the manuscript relegates Hedda to the background, excluded now from her supposedly loving husband's life. This slap in the face, and not merely the Judge's attempt to blackmail her and coerce her into an affair, brings about the catastrophe in the end.
In summary, I would say Hedda's behavior is, in fact, more rational than pathological, in spite of its destructiveness. She has been placed in a situation where the acts of those closest to her—her inadequate husband Tesman, the irresponsible and dysfunctional Lovberg, and the ruthless Judge Brack—make it impossible for her to find any normal fulfillment. That said, the streak of very real narcissism in her character makes it impossible for her to compromise, to find her way out of the corner she's been boxed into. And so, tragically, her only option is suicide.