Trousers for young girls - or often jumpsuits, I suppose - weren't actually that outrageous in this time period, though I suspect busybody men who are too invested in other people's clothing never really go away either. Actually, it being specifically 1945 might have something to do with it. Women started wearing trousers when they began working in factories during the war and there was a lot of backlash when the soldiers came back and found that the housewives they'd left behind were working and earning their own incomes.