In reply to this whole Quiet malarky, in my view, I don't see her as sexual, or really sexualized, sure the outfit could have been a bit more supportive. But I wouldn't class her as being specifically a "hot bikini babe" as she looks much more like an average every day woman in her late 20s with no makeup and nothing (aside from the outfit) to suggest anything other than her being reserved.
The plot and the reasons for this could make sense of it. The way I see her is that she seems like she has been through some seriously bad situations either ingame (torture) or pre game, such as child abuse or slavery or rape etc. So I hope her character aspires from people who have recently been in awful situations and have some complex psychological reasons for acting in a certain way. Being it her own choice to dress that way, either out of habit from being in captivity or to take power from what once would have been humiliating.
That said, it still doesn't change the fact she isn't wearing much, and even for a prisoner or someone who could have just escaped a jail even if they were naked during captivity it does not explain why she would not have stolen a guards clothes (like meryl did) or have had more left of her original clothing.
Either way, it draws attention to the game, good or bad, it gives them publicity. I doubt (or at least hope) this is only one section of her storyline.
But in my eyes, a bikini on a non ugly woman alone shouldn't be classed as sexist or overly sexualized as it is far from it, even if it does seem a bit silly to reveal a character in that tone. It gives off the wrong impression.