"A fallen woman" (and variants on falling connoting moral decay/sexual license, eg "she fell" "she had fallen to a seducer," etc.)was in usage in the US, certainly from mid to late 19th century. It was used for prostitutes as well as women who had sex out of wedlock. You might not want to strain yourself looking for a perfect, exact distinction between prostitute & sexually active woman, as folks then didn't generally distinguish. Look at the ruckus Ben Butler stirred up with General Order No. 28.