Well, unfortunately the world will never be completely safe and I mean this on a broad sense in regards to a series of stuff that could potentially harm a child. From a set of stairs that is dangerous to them when they are very little up to piss drunk drivers when they are in their late teens.
Nowadays we have the internet and our young ones are often online way more than they should (I mean, let’s face it, I am in my thirties and I think I spend more time online than I should and I am sure most preteens and teens spend twice as much time online as I do).
With this new ‘territory’ comes lots of good things like the ability to connect with people you would never meet before or even a vast amount of content and information for school related stuff and such. Of course new challenges and dangers are also part of the mix.
I don’t know how old your daughter is but you did mention she was a teenager. It seems a bit too excessive, and please pardon me if this sound insulting but it is not the intention, that she is clueless still regarding sexuality and sex. I mean, I will take this ‘teenage daughter’ with a grain of salt given she still believes that babies come from kisses and I will probably guess she is a preteen around her 11–12 years old (given your age of 33 as well).
I think it is massively important that you explain this things to her. She will not lose her innocence by finding this stuff out. I mean, as you said it yourself, some creep is already teaching something to her about this but in the wrong way. At least teach her the truth on the matter and let her understand all of this (sexuality I mean). With the more information she has on her hands the more able she is to keep herself safe.