Ok that's just really bad design.
I've mostly concluded that the artist has shoddy taste, especially in key-art portraits. Which is a terrible pairing, considering the job. When they're on a series with characters I care about, I find examples of that shoddy work extra annoying. It bothers me when conversations are herded around the idea that "the designs are bad because of big boobs." It's much more than that.
Oh, a perfect example just popped up. Insincere or just plain oblivious posts like this. This train of thought is barely worth responding to, when you break it down:
So you really, seriously believe that there are no woman out there with this large natural breast?
I mean, I know I'm in a difficult position with what I said and not everyone can agree on that, which is totally fine, but this is nonsense, I don't know what to say, answers like this just make me speechless.
The above premise is a rhetorical device; it isn't tied to the character design, and is barely intelligible as an extension of the conversation behind the thread. It's posed as a strawman.
Frankly, looking back to their original comment:
What do you have against woman with natural big breast?
Did they not deserve to exist in videogames at all? Just because they have big breast? Isn't that not kind of sexist?
She is not even naked, come on.
This person is either playing sardonic as a bit, or is so far gone, they're not worth the breath. Again, it's so obviously in the "acting aghast" routine, using the format of "ha! you're actually being sexist because you don't see women as equals enough to act sexist toward them!"