I 19[M] let my 18[F] girlfriend blow another guy?

So we were hanging out at my and roommate’s place. We were 4 guys and 3 girls and we had a movie marathon in the living room while drinking and smoking a bit.

I was sitting on the far left side of the couch, my roommate’s friend on the far right side and my girlfriend inbetween. Throughout the evening she kept adjusting her sitting position and going back between him and I kind of. So for, so normal. But towards the end of the night during the last movie, she had her head more or less in his lap and her feet in mine.

At one point she laughed and said she can feel that she’s laying on his dick. He asked her if she approves of the size and she responded that she can’t really tell. After some back and forth banter between them, she asked me if it’s okay for her to check it out. I laughed and shrugged and said that I don’t care in a semi joking way. Half expecting she was just joking as well and wouldn’t do it anyway, half masking my jealousy while trying to play it cool.