Is the consent of her guardian a condition for the marriage of a mature, sane woman, even if her family knows that she is old? And can she marry herself off?

A woman's marriage without a guardian (wali) is invalid according to the majority of scholars, whether she is a virgin or previously married, young or old, due to the Prophet's (peace be upon him) saying: "Any woman who marries without the permission of her guardian, her marriage is invalid." If the guardians refuse to marry the woman to a suitable suitor, she may refer the matter to the شرعي (Sharia) judge to marry her.