Is it permissible to break off an engagement to a woman who refuses to sign the marriage contract, describes her fiancé as stubborn, argues a lot, rejects the opinions of religious scholars, and believes she doesn't need to ask anyone because she knows right from wrong?

It is not permissible to prolong the engagement with the fiancée, because she is a stranger [non-mahram], and this has negative consequences. The claim of insufficient acquaintance to delay the marriage contract is incorrect, and the engagement period does not achieve the true acquaintance required. The fiancée's statement that she does not need to ask scholars because she possesses intellect indicates ignorance, for intellect is not a legislator, and one must ask the people of remembrance [scholars]. We advise you to be frank with her about her mistaken thinking. If she responds positively, then complete the marriage contract. If she does not respond, then you must turn away from her.