Is a girl who drank poison to threaten suicide and died in the hospital considered an infidel, and what deeds are required to intercede for her in the grave and the Hereafter?

The creed of the Ahl al-Sunnah wal-Jama'ah (Sunni Muslims) is that those who affirm monotheism (Tawhid) will not abide eternally in Hellfire. The threat of eternal damnation for one who commits suicide is understood as a deterrent, or applicable to someone who considers such an act permissible (i.e., halal). The act committed by this girl, taking her own life, is a grave sin. However, she is still considered a Muslim, and the rulings pertaining to Muslims apply to her. Therefore, funeral prayers should be offered for her, she should be buried in a Muslim cemetery, and prayers for forgiveness should be made for her. Seeking forgiveness, supplication, and giving charity on behalf of the deceased are beneficial for the departed.