Re: Suspecting daughters friend is being sexually abused

Blue Rose is spot-on.  You also didn't mention the ages of these children.

I would agree to ask about the specific website, and to speak directly to the parent(s).  It may be that the little girl has an older sibling giving her some bogus information about reproduction, or it could be that the little girl has her own interest in reproduction, or (worst scenario) it could be that she actually has seen images that she's not mature enough to process. 

I would just suggest keeping your ears and eyes open, and paying attention to language and body-languages before jumping to conclusions.  Having said that, I would also suggest that you keep your observations as covert as possible without demonstrating any concern or panic with regard to this issue.  Don't go "fishing" for information with prying questions and suggestions, either - this can backfire on someone who isn't trained to seek answers from children and a child will certainly report back to their parent(s) that they are being questioned.  Allow the child to open the door of information - a child will always make disclosures, regardless of whether or not they have been schooled to keep their mouths shut.

Brightest blessings!