Mich. Comp. Laws § 557.25

Sec. 5. A married woman may act as a surety for the debt or obligation of another person, including the debt of her husband, by signing a written instrument providing for the suretyship. A judgment entered against the married woman as a surety may be satisfied out of her separate property as described in section 1, whether or not the contract of suretyship benefits or concerns that separate property.