She can't have been Danish.and She must have been Swedish
Danish,Swedish是形容词表人或语言.而不能表国家
【她不会曾是丹麦人,她肯定曾是瑞典人】
【她以前不会是丹麦人,她以前肯定是瑞典人】
丹麦:Denmark
瑞典:Sweden