What was a "Dolly mop" and who did the author consider one?

A "Dolly-mop" was an amateur prostitute, that is, a woman who had sex with a boyfriend or lover in return for a few presents or a little money. The author seemed most shocked that such a person would have sex merely for her own pleasure. Some nursemaids and servant girls fell into this category, meeting men in parks on their days off. Others were kept by soldiers.