What is the ruling on the prayer of one who doubted the invalidation of his ablution more than once, then began to pray, and after finishing it, doubted its humility, then intended to repeat it but found the beginning of menstruation? And must she repeat it after menstruation?

The cure for obsessive whispers (waswas) is to ignore them and pay them no mind. If you doubt that something has exited, do not repeat your purification (tahara) or your prayer (salat) unless you achieve absolute certainty. Your prayer is valid, and you are not required to repeat it. The absence of khushu' (devotion/humility) does not invalidate the prayer, and repeating it on that account is not legislated. Regarding incontinence (sals), it has its own specific rulings and what the affected person should do.