I don't get this. So, she isn't a policeperson, but she is a "confidential informant"? Like she solicits sex, and then turns the john in? Or maybe only if it's not enough money? (I have no idea, is $200 for sex a lot of money, or the market rate, or what?)
"Confidential Informant" = criminal who agrees to help police arrest other criminals, in exchange for leniency/immunity for her own criminal acts.
Which customers got arrested versus which didn't? My guess is that, since being convicted of soliciting a prostitute in PA carries fines of up to $10,000, a customer with the assets to quietly plea bargain to pay up as long as there's no jail time would be the most lucrative arrest for the system.