Is a wife obligated to fulfill her vow after her husband has fulfilled his, and is she permitted to pay it in installments?

You must pay the liras you vowed, and what your husband paid is not sufficient, because each of you made an independent vow. This is based on the saying of the Messenger of Allah, peace and blessings be upon him: "Whoever vows to obey Allah, let him obey Him; and whoever vows to disobey Him, let him not disobey Him." It is permissible to pay in installments, unless you vowed to pay it all at once.