That's a very good and interesting post, joeboygo.
I think that "maternal instinct" and "harvest" are key to understanding what motivates Irisu.
I think that one of the key, defining traits of Irisu is a very strong sense of responsibility. She feels a "maternal instinct" towards any project that she believes is her responsibility to see through to fruition.
There's an old saying of "A mother will do anything to protect her child", and I think it is here where we see why Irisu is willing to take morally questionable acts to protect "her babies" (i.e. the projects that she feels are her responsibilities).
However, Irisu has "sensitivity to others' feelings" and hence she searches for win/win solutions. Or, at least, solutions that won't hurt people. This is why buttering people up is an approach that Irisu likes - Because she views it as harmless, and perhaps even helpful, should she manage to pull it off effectively.
And I agree with you that Irisu uses "feminine wiles" but in a
seemingly subtle way meant to make the other guy feel like a million bucks without using anything all that explicit. This use of her femininity is perhaps in line with the "ideal of femininity" aspect of the Empress Tarot Card.
Irisu's key flaw is probably in underestimating the perceptiveness of others. As "an Empress" she kind of views herself as above it all, since she sees herself as somebody who's separate from the average person because of the responsibilities she has. This can create a bit of a blind spot for her, as we saw in her arc.
But even so, she can be extremely effective and smooth, and her strong sense of responsibility is one thing I like a lot about her. If Irisu was a Captain of a ship, she would
never abandon her ship.