The upward bump at the top is the line between her breasts, you can see it in the painting i linked too, but the logo is black and white so it is more obvious. It could be thinner but seems that all lines on it were drawn with the same width. The upward bump at the bottom is the silhouette her breasts are making on her right forearm as a background. Imagine if [1] or [2] was tilted a bit forward and the right forearm was below her breasts. In both of these paintings the breast silhouettes are visible due to shading even though the colors are soft and they aren't tilted like the woman in the logo. Again since the logo is black and white it makes the silhouettes more pronounced since it relies on them for definition.
The black below is her arm from the elbow to the hand. The hand is just at the bottom right of the image with the line going in a /| shape right below the elbow of the left (right as we see it) arm. The tip is the fingers. They look a bit too long but i think it is mainly due to the line width.
The anatomy could have been better (the neck is a bit too long, the left shoulder is a bit too rotated, the left upper arm is a bit too short) and a couple of lines are too long that can be distracting, but overall it is very obvious to me that this is a pose with a tilted head, right arm on stomach and below breasts touching the side/back, left arm rotated a bit forward, on top of second arm with a slight angle in the elbow.
I mean, it could be a bikini but it also could be a dress like in all the images i linked at. There is not enough detail to say one way or another, the only hint is that the image is inspired by 40s pinup posters and at least from a Google Images search one or two had girls wear just a bra or bikini. All others use full clothes and dresses.
[1] https://muscleheaded.files.wordpress.com/2015/11/frahm.jpg
[2] https://www.ebay.com/itm/1940s-Pin-Up-Girl-Glamour-Shot-Pict...
