Base the Third

I'm not quite sure how to even begin telling this.
Today I was in French class, with my friends... let's call them Sophie and Aditi. (They'll never see this, but I still don't wanna use their names.) Sophie and Aditi are better friends with each other than they are with me, but I'm kinda used to it at this point, and I need someone to sit with while learning forms of the passe compose, so there I am. 
Aditi has three main possessions: an iPhone, a tendency to talk too much, and a nerdy boyfriend called... um... Dan. On this particular day, the first two got her sent up to the Seat of Death, beside the old-fashioned light projection machine our broke school still uses, to work alone. Sophie and I were still at the back.
So we kept working on our passages about someone's adventures in town with their friend Isabelle for a few minutes, then Sophie started writing something on a bit of paper. I kinda assumed that she's going to get up and give it to Aditi when she's done, because they do that kinda thing all the time, but she waited until the teacher has prowled past and slid it over to me.
Did Aditi tell you she got to third base with Dan?
I had to read it about three times to even BEGIN to get that through my head. Third base? THIRD BASE? THIRD MOTHERF***ING BASE??? Sophie took the paper back, wrote some more and slid it back to me. You know what that is, right? (Everyone thinks I'm the innocent one, since I still look like I'm about 11, but I do notice shit.) Hands and mouth on the hoohah. Don't tell anyone else, idk if Aditi is ok with people knowing.
The thing is, I've known both Aditi and Dan for several years. Aditi at third base, I can almost come to terms with that, but Dan??? WHAT THE WHAT??? I can nearly process... hands... but mouth? At that point my brain kinda shuts down from sheer nope nope nopeity NOPE. It's impossible to look at two people you've been seeing for four years and imagine them doing that stuff together. We're all fifteen, people. Meaning that not only are Aditi and Dan's adventures in hoohah-land completely un-processable, they're technically illegal.
I'm absolutely not condemning either of them for doing that stuff. If they both want to, and they feel comfortable, then um... why the hell not? I just can't really get my head around the fact that I've never even held hands with a guy (or girl), and Aditi and Dan may have already done the deed.
I just... hope they keep it safe and consensual and as private as they want it to be.