Is a mother's obedience obligatory in refusing to marry a young man of faith and good character, or is disobeying her considered an act of disobedience, especially if the refusal is due to a difference in nationality? And is the daughter sinful for refusing to marry anyone else, fearing that she might not fulfill her marital rights?

If the aforementioned young man is religious and well-mannered, the mother should not oppose marriage to him merely because of a difference in nationality. One can continue trying to persuade the mother and involve intercessors, while increasing supplication. If the mother refuses without a legitimate شرعي reason, the guardian may marry off the daughter, and if the guardian refuses, she may refer the matter to the شرعي court. It is possible to obey the mother and forgo marrying him to please her. If the marriage to him is not completed, the relationship with him must be cut off, as he is a stranger (non-mahram). Marriage in general should not be abandoned, as it may become obligatory if temptation (فتنة) is feared. Overcoming attachment to this young man is possible for one who is determined, along with entrusting the matter to Allah Almighty and asking Him for a righteous spouse.