Isn’t she adhering to the dress code?
Choosing swimwear can be a pretty fraught dilemma for many women, for a multitude of reasons. It is easy to overthink what they look like, who is going to be looking at them, and whether they are going to be able to enjoy themselves at the beach or pool while wearing significantly less clothing than normal. It is enough to drive anybody crazy, and it makes it all the more commendable when somebody is able to just put on the bikini and forget about it all.
There are valid reasons for women to be neurotic about it, though, and mostly these come from the unsolicited opinions of other people. They believe that they should be allowed a level of control about what they choose to wear. While it might be true that there is a time and a place for certain bathing suits, being overly obsessive about the clothing choices of others is rarely a good look. It makes everybody involved feel awkward, and even if the bathing suit police think that there is a moral reason for it, it is often eclipsed by their outsized reaction to what is little more than some pieces of fabric.