Even if the girls got tested before getting hired....She could be infected with something before she got the test.....but it usually takes at least a week upwards to a month before the disease/infection/virus causes symptoms and actually be detected..Theres always an incubation period.....And as for herpes, majority of clinics don't even test for that shit unless you have an outbreak...They'll take a culture of the puss and see if its the herpes virus....Otherwise, the tests that DO test for Herpes virii, are very unstable and about 50/50 when it comes to false positives.
You don't wana catch a STD? Use a rubber when you fuck and don't put your dick in a nasty mouth.. All the girls who have sucked my dick, have let me inspect their mouths before I shot massive loads down their throats....I have literally said "Open your mouth and let me check it out.." Obviously no cold sores on their lips...but Just checking for any ulcers/blisters or anything inside the mouth..I don't want my dick touching that shit..You can even turn it into a game of Playing Dentist..."I have to examine you before I drill you

" lol Sounds dumb, but as long as you're straight with em, and keep a cool/funny vibe going on....they'll comply