Eva is actually a well written character though compared to b&b and quiet. As for eva showing her boobs, thats because she knows that shes a spy and that an easy way to manipulate snake is to play the part of the femme fatale. Its in line with evas character to do that. Its why it works compared to quiet who does the same thing but has no character to her.
That's fair. The difference between Eva and Quiet is better justification. But that's not why for real, it's just why in the fiction. If she didn't it wouldn't take away from her character, but she does because Kojima needs skimpy ladies. Hell, I bet anything that the next Death Stranding trailer has some model or actress in skin tight or no clothes and lingering camera shots.