Is it obligatory for someone who dreamt that they were fighting alongside the Messenger of Allah, peace and blessings be upon him, and with Umm Habibah, and that they were called by the name "Hatim" despite being a girl, and saw someone wanting to kill them, and that the Messenger gave them a staff, not to tell anyone and to fast for three consecutive days?

This is a good vision and glad tidings. It is recommended to praise Allah for it and thank Him, and to follow the Messenger, obey him, and strive against one's self. There is no harm in narrating it to loved ones. It is not obligatory to fast three days or even one day because of it. "If any of you sees a vision that he loves, then it is only from Allah, so let him praise Allah for it and narrate it."