I also find it bizarre that she was filled with self-loathing for contracting a disease, not for the behavior that caused her to contract the disease.
Getting a disease is not immoral, it’s just a possible consequence of certain behavior.
It should also be pointed out that to catch a disease it is not necessary to live up to the modern definition of “slut,” which I assume is “excessive sleeping around.” Presumably, a “normal” amount of sleeping around is fine.
To get infected, only a single act is necessary.
IOW, a girl could in theory lose her virginity and at the same time get pregnant and contract half a dozen diseases, some of them incurable, from a single act of fornication.
Same for a guy, of course, except he probably wouldn’t get knocked up. :)
Contracting the disease is just one way of “getting caught.”
I understand your point. Society’s judgment is triggered by the consequences - pregnancy or disease - and seems to send the message not that screwing around is immoral, but that the girl should have managed it better.