"Certain types of girls who gives boys the come on" "class tart" etc
. Really appalling language and anti-feminist, shaming sentiments to use about any women and in particular young teens (that you know absolutely nothing about). I do hope you no longer work with any, because I occasionally do , and you'd be sacked if you spoke that way in the workplace. I'm not sure you'd get away with it discussing adult women that way either- not anywhere I've worked, or ever socialised, at least.
You seem very angry and embittered about what certain 'types' of females are up to
. I think it's more important to focus on the safeguarding of both children, who sound naive and are young, rather than psycho analysing a teen girl we've not met and apportioning 'blame'.
I would certainly make it my business to make contact with her parents re: the issue OP, then they can hopefully support their daughter through the reasons she wants to and if it is a good idea/how to stay safe physically and emotionally when doing such a thing.
13 is so young but I remember it being the same in school. So frustrating that we grow up, realise we were wrong and it was far too young to be doing that, try to tell the next generation and they don't listen either, on a loop! I'd focus heavily on a talk with my son about consent and respect, and that he must ask her at each stage if she is ok, that she wants to, that she is not in pain etc. I would point out to mine that just because she says she wants 'x' doesnt mean she will when it happens, or that she will like it and have to see it through- the same as he has no idea about how much he would enjoy things he's never tried. Arm him with the tools to create a situation that isn't damaging, and hopefully her parents will do the same. I would also reiterate any previous sex education as regards how pregnancy can happen and they are not immune, and ensure he has access to condoms if it came to it. You don't want a pregnancy as a result of embarrassment about sourcing them at the end of the day.
Tbh I would also try to limit any alone time they have, and certainly wouldn't offer them any at 13 but ultimately if they want to they will, as many before have done. Tricky situation for you OP.