By the time this comic came out Dell had been cast adrift by Western Publishing, which held the cartoon licenses. It was an interesting time as the company raced to toss everything at the wall hoping that something would stick. They ended up in producing fascinating comics, many of which wouldn't have passed the Comics Code, or the Dell Pledge to Parents for that matter (violence, mild horror, revealing clothes, characters saying "My God!"). Nothing too extreme, but at the time titles like Mike Shayne and Private Secretary felt a tad more grown-up than other comics. Like Code comics and Western/Gold Key, Dell steered clear of suggestions of sex. Which brings us to the bikini--Code or no Code, someone in Editorial obviously had a hangup about "going too far." He or she (probably he) couldn't imagine showing even a modest bikini.
However the expressions on the crowd's faces combined with our the fact that our heroine is shown bare from just above her breasts, without shoulder straps, strongly suggests that Cynthia is in fact stark naked. "Wowie! No hidden secrets!" Not the intended impression, I'm sure, but the reference to her bikini in a later panel sound like coy sarcasm.