I believed the passive is just a name & intended to be not working

You can check by putting her in your formation

During starting of battle, you can see that her passive "The Great Tiger Descend the Mountain" did not appear on the screen (left side) like other character passive when trigger

Unless the passive add some hidden stat that we never know

It doesn't do anything at all, it's just for fun. Same as many other New Year ninjas' passives.

Yeah its just typo that does nothing, but I wish they change it because that ninja is pretty decent to use but she has no passives :/