What is the ruling on one who is praying and feels the onset of menstruation during prayer: should she interrupt it due to doubt, or complete it and verify after the salutation?

The emission of menstrual blood invalidates ablution (wudu') by consensus (ijma'). If it occurs during prayer, the prayer must be interrupted. However, if a woman doubts its emission during prayer, the default assumption is non-emission, so she should not interrupt her prayer unless she is certain of its emission. This applies to all nullifiers of ablution, based on the Prophet's (peace be upon him) saying: "He should not leave (the prayer) until he hears a sound or finds a smell."