I think it could have gotten her arrested even on many public beaches. But in her street clothing as Diana Prince we've seen, she's entirely in keeping with the accepted norms of the period. I'm curious whether the movie will portray her in her costume in social or formal settings, and not just in very dangerous conditions where onlookers are too busy trying not to get killed in the fighting to be scandalized by what she's wearing.
Setting aside the notion of men being less likely to accept a woman fighting in a war (until they realize it is an indestructible woman fighting on their side), I'm not 100% sure of that myself. The early 1900s were an interesting time in history for (women's) fashion, and while I'm not an expert I do know that there were some rather maverick stuff going on at the time, particularly among the aristocratic Europeans. I mean, ironically you probably would get arrested at the beach for wearing this:
But it would be "daring" at a dinner ball. And I don't know who was supposed to be wearing this anywhere in circa 1910 Europe:
But apparently someone was, as it dates from that period. Prior to the war, there appears to have been a kind of fascination with appropriating "exotic" i.e. "foreign" stylistic touchstones and incorporating them into high fashion. Far eastern and "oriental" influences seemed to be in vogue. This was apparently actually an advertisement circa 1910:
So it is possible that at least among the aristocratic Europeans, Wonder Woman's costume would be seen as "scandalous" but in a "well, you know those foreigners" kind of way as opposed to a "oh my god protect the children" kind of way.
