as said, great point. i think this doesnt have any intentional bearing on the story. to me it's a frustrating aspect of the series, akin to the lack of communication between the good guys. in fact, this is another example of failure to communicate. but it's so frustratingly stupid.

the only way to explain her failure to talk requires speculation, rather than taking it simply for what it is.

i think her reluctance to reveal herself is supposed to cover her noncoummunication. but given the stakes involved, it is not plausible that she would remain silent.

a renowned and historic hero over the ages doesnt reveal everything she knows that can help the good guys save the world--because she doesnt want people to know who she is?

Moreover, she could have preserved her identity by telling the people who do know her and have them communicate/take action.