Younger than eighteen? Really? Seriously? We all explained the facts of life to my niece at age nine because she asked. A good rule of thumb: around 8 - 11 or 12 or so tell them the full truth but ONLY if they ask. By age twelve they should know everything because they are old enough to get pregnant and should be in possession of all facts, including use of protection and birth control, just in case.
It seems like you're older than your friend. I'm guessing she's older than 8 but no more than 11(since she's asking questions like that) & it sounds like you know the answer. It's not your call to tell her about these things. It's her parent's. You already messed up by telling her to google it, so I suggest you make things right & tell her mom. Also tell her mom wat you told your friend (about searching in the computer) that way her mother can be wary about wat she is doing in the PC & keep an eye on her, since your friend is gonna get more & more curious!