What is the ruling on one who feels disbelief in the Last Day, even though his mind acknowledges its necessity for the realization of Allah’s justice, while his heart does not believe it?

Upon reviewing the previous questions from the questioner, it becomes clear that she suffers from waswasah (obsessive whispering) concerning matters of disbelief (kufr). The cure for this is to stop thinking about these matters, not to dwell on them, and to completely turn away from them. The contradiction she mentioned between her mind and heart is one of the effects of waswasah. There is a difference between doubt that leads to kufr and waswasah.