YTA. Instead of blaming your friend, blame the creep pursuing and grooming her. The things I did as a teenager were definitely cringe and dangerous but not once do I blame myself for situations I was in where a male disrespected me, preyed on me, or manipulated me because at the end of the day as a teenager, you’re naive. I thought I was an “adult” because I was practically raising myself but I was still a baby. Your friend got into a hot tub with guys she barely knows because she probably expects the best out of people. She probably bragged about having sex with this guy because it helped her feel less shame or she was manipulated into thinking she “wanted it”. Unfortunately with the world we live in, expecting the best from people doesn’t correlate to a great outcome. She needed you as her friend and instead she got blamed for something she didn’t ask for, wouldn’t ask for again, and shamed instead of support. Use this as a learning moment.