Absolutely speak with her about your knowledge of the sorts of web sites she has been viewing. This needn't be a drawn-out discussion. Clear and simple is best. Let her know such web sites are 'out of bounds' and she is not to view them.
Thank you for your replies. I have already relocated the computer from the room to the family room thereby eliminating the "privacy" issue. But can anyone please advise me as to what to do: "forget" about what happened and hope the new location of computer causes her to deter from such sites ... or talk to my daughter to make her realize what she did was bad.
I'll appreciate further advice. THANK YOU
Of course yelling/screaming is not useful, but there is planty of room for intervention between the extremes of yelling and doing nothing. In fact, you won't be making a mistake if, in general, you never yell and scream - that is simply not a reasonable way for anyone to behave. To the point you raise: simply set a firm limit by telling your daughter that such web sites are not allowed. Set the parental controls on your computer. And please do not permit computer use in her room - it just invites problems at this age. Later, during her teens, there will be time for that. But she's too young.
No computer in her room. The computer needs to be where there is family traffic and you can easily see what she is doing. You can also setup software that allows you to specify which web sites she can go to. If this is installed she is not able to go to other sites.