I'll repeat what I said on the other thread: this is not about 'boys', this is about totally inadequate supervision. It was obvious from your last thread that this mum would not supervise.
Children who want to push boundaries and take risks - boys and girls - will gravitate to places where they know no-one is watching... and this mum's house sounds like one of those places.
Other mixed sleepovers would have been different, happy occasions. I can vouch for it, having hosted, permitted and (in my own teenage years) attended many.
There are very many other boys who would never behave like this. I am sure I'm not the only parent of a 13yo who is shocked, saddened and offended by the implication that they are all porn-crazed predators.
If you raise your daughter to have such low expectations of all boys, you do her a huge disservice, as well as them.
The 'rule' you need to teach your DD is not "beware of boys" but "beware of unsupervised strangers". I would not feel safe sleeping in a room full of people I did not know, and nor should she. But if she is lucky enough to have good male friends, whom she can trust, then she's fine.
Even if you wanted to, you could not keep her away from boys forever. You need to help her learn to judge character, and to take action to get herself out of situations she doesn't like. The most worrying thing about what you describe is that your DD found herself in a situation that made her uncomfortable, and didn't know how to get out of it and/or ask for help. You need to help her learn this absolutely essential survival skill, fast.