Is the questioner considered a disobedient daughter to her mother because her mother is displeased with her daughter's marriage to her cousin, and what should she do regarding her decision to cancel the marriage?

If the mother's rejection of the suitor is only due to what was mentioned in the question, then her obedience in abandoning him is not obligatory as long as he is suitable, and the girl is not considered disobedient by disagreeing with her. However, it is not advisable to disagree with her. It is obligatory to be dutiful to the mother, to treat her well, and not to cut ties with her or harm her. It is preferable to leave the suitor to please the mother if no harm results from it, and there is no sin in breaking off the engagement for such a reason.