I have always admired Idril. Given that the preparations were largely in the event of Turgon's death and she was the rightful heir - or mother of the heir if a woman was considered unfit
I think coup d'etat is not quite the situation. I do see that it could look bad especially since Turgon's weakness was his faith in the strength of Gondolin.
I have always thought of Idril as wise and resourceful and motivated by the good of her people. Tolkien's blondes are so much more interesting than the brunettes
