Must I fulfill my wife's vow, which she made without my knowledge, and is her vow valid?

Celebrating the Prophet's birthday (Mawlid) is an innovation (bid'ah), and vowing to celebrate it is a disobedient act that must not be fulfilled, for the Prophet, peace and blessings be upon him, said: "Whoever vows to obey Allah, let him obey Him; and whoever vows to disobey Allah, let him not disobey Him," and: "There is no vow in disobedience to Allah." However, if your wife made a lawful vow, she must fulfill it, and no one else is obligated to.