I know that tradition lists 7 women prophets, and I think Esther is listed as one of them.

It is easy to see that Sarah was a prophet (for example, in Vayeira during the telling of the expulsion of Ishmael it is even mentioned in Rashi that Abraham is informed that her prophesy is even stronger than his own). It is even easier to know that Miriam was a prophet (Moses tells Aaron and Miriam that his interactions with Hashem are different than theirs, which implies that they too heard the voice of Hashem). And I think Deborah also, you can find source in the Tanaach that she was a prophet. And certainly Hannah (who mentions Israel's kings before there were any). And obviously Eve, who Hashem talks to directly in Bereishis.

But the book of Esther gives no hint (that I could discern) that Esther heard the voice of Hashem.

So from where do we derive that Esther was a prophet?

I know that tradition lists 7 women prophets, and I think Esther is listed as one of them.

It is easy to see that Sarah was a prophet (for example, in Vayeira during the telling of the expulsion of Ishmael it is even mentioned in Rashi that Abraham is informed that her prophesy is even stronger than his own). It is even easier to know that Miriam was a prophet (Moses tells Aaron and Miriam that his interactions with Hashem are different than theirs, which implies that they too heard the voice of Hashem). And I think Deborah also, you can find source in the Tanaach that she was a prophet. And certainly Hannah (who mentions Israel's kings before there were any). And obviously Eve, who Hashem talks to directly in Bereishis.

But the book of Esther gives no hint (that I could discern) that Esther heard the voice of Hashem.

So from where do we derive that Esther was a prophet?