Are diseases of the heart such as showing off (riyaa') and conceit ('ujub) considered hypocrisy (nifaaq), especially since the questioner is newly repentant and fears that every good deed she performs or attempt to better herself is hypocrisy, and do the Quranic verses that speak of hypocrisy apply to her?

Diseases of the heart are dangerous, and the effort to repel them is more important than treating physical ailments. One must not give in to the whispers of ostentation (riya') and self-admiration (ujb) so that they do not hinder worship. At the same time, one must not neglect the heart and its rectification, and seek help by reading the books of trustworthy imams on this matter. Your fear of hypocrisy (nifaq) is a good sign that motivates you to rectify your actions and your heart, but it must not turn into a pathological fear that prevents you from performing good deeds and acts of worship.