Is it permissible for a committed, veiled Muslim woman to attend religious meetings of the "Jehovah's Witnesses" group with the intention of inviting them to Islam, while fearing that her presence might be misunderstood as dissatisfaction with her religion or that it might be a trial (fitna)?

You must safeguard your religion and avoid sitting with these women or attending their gatherings, especially if you are not sufficiently knowledgeable in Islamic law or confident in your ability to influence them and refute their misconceptions. You can resort to other means of inviting to Allah in cooperation with believers, such as online communication or disseminating Islamic materials.