Has the questioner broken her oath by saying: "By Allah, there is no joy in disobeying Allah," after it occurred to her that some people feel pleasure in disobeying Allah?

There is nothing upon the swearer, because he may be truthful in his oath if he intended to deny true joy from the people of disobedience, which is the joy praised by sacred law, like rejoicing in Allah's bounty and mercy. However, if he did not intend this meaning and thought that the people of disobedience do not rejoice in it, and then the opposite became apparent, then there is no expiation upon him, and his oath is a laghw (unintentional/null) oath.