Does a sin befall me for refusing my neighbor's request, after I swore by Allah, even though I need some non-essential items?

It is clear that the questioner is afflicted with obsessive-compulsive disorder (waswas), and she must stop indulging it and turn away from it. There is no blame in what she told her neighbor—that she does not want anything—even if she was in need, provided she intended dissimulation (tawriya), meaning she intended a different meaning than what the neighbor understood, or that she did not want that particular thing from her at that moment. This is not a lie because it is an expression of not wanting, not of not needing.