What is the most legitimate and appropriate way to treat demonic possession (mass) or sorcery (sihr) to ensure that the symptoms do not recur, and should my niece make up the missed prayers for the days she was ill and unaware of herself?

Allah tests His servants with illnesses as an expiation for sins and an elevation of ranks. He also legislated seeking treatment, as narrated in the Hadith (definition): "Seek treatment, O servants of Allah, for Allah has not created a disease except that He has also created its cure or remedy, except for one disease." And upon whoever Allah has granted recovery, it is incumbent upon them to fortify themselves with remembrances (adhkar), Surahs Al-Ikhlas (definition), Al-Falaq, and An-Nas, and Ayatul-Kursi, and to frequently supplicate for well-being, and to attach their heart to Allah, for "nothing harms except by Allah's permission, and nothing benefits except by His permission, Glorified be He." As for the one who is bewitched or possessed and has lost their mind, there is no responsibility upon them, nor any sin, and they are not required to make up prayers or fasting, based on the Hadith: "The pen has been lifted from three: from the sleeper until he awakens, from the child until he reaches puberty, and from the insane person until he regains his sanity."