Go into Lilly's room without locking the door

I slip into her room and close the door behind me. I turn to see Lilly looking at me with a stunned look on her face. I then realize she must have heard me when I shut the door. For a few moments, we just stare at each other. Then, Lilly slowly starts to smiles as she motions me to move between her legs with her finger. I’m not sure what exactly she wants, but I have a good idea from what I heard her moaning earlier. So, I climb on the bed and crawl between her legs as she spreads them for me. I gently kiss the inside of her left thigh and slowly kiss my way up as I feel her shiver with excitement under my touch. I reach her moist wet lips and softly breathe on them which cause her to moan. I then start licking her lips from bottom to top and back again. As I lick her, I listen to her moans to find out what spots she likes to be licked at and focus my attention in those spots. After a while, I have narrowed down the spots she really enjoys and I can tell she is really enjoying it by her heavy breathing and moaning. I can feel her starting to tremble even more as she presses down on my head with her hands. She then starts to moan loudly as I can feel and taste her juices flowing out of her. Her orgasm hits hard and she shakes the bed as she groans and moans.
I then stop and look up at her smiling down at me and she giggles. I then realize I have her juices all over my face and likely look like a mess as well as my hair being everywhere from her pushing down on my head.
It’s then that I hear the door opening. In fear of being caught, I hop off the bed and roll underneath it as I hear the door open all the way.

Male voice: “What’s going on in here? Who was with you?”
Lilly: “It was no one and can’t you see I’m naked? Get out of my room.”
Male voice: “Not till you tell me who was in here with you. Wait are they still in here?”
Lilly: “Brad, get out! There isn’t anyone in here!”
Brad: “I should tell our parents about you sleeping around. I’m sure they would love to know their precious girl isn’t a virgin.”
Lilly: “I am too a virgin!”
Brad: “I doubt it. I think I’ll look around your room and find the guy that was in here.”
Lilly: “Please, stop. I’ll do whatever you want.”
Brad: “Anything?”

I guess she nods because I don’t hear her response to his question. I do however feel the bed move right before I see a pair of pants drop next to me on the floor. I wonder what they are doing, and then I hear muffled moans from Lilly as if something is in her mouth. Wait, is Brad having his sister give him a blow job? I listen for a minute or so and then hear Brad grunting. I guess he is getting a blow job. The moaning and groaning stops a couple minutes later after it began.

Lilly: “I thought you wanted to cum and then you would leave.”
Brad: “I want to do something else first.”
Lilly: “Brad, please, not that. I want to give that to someone special.”
Brad: “Looks like I’m going to be that someone special then.”

What do I do? I’m not sure, but it sounds like Brad is about to take Lilly’s virginity. Should I risk waiting and hop he comes to his senses? Maybe someone else will come. What about Brad’s girlfriend Ashley?