What Do I Do?

My sister and I are very close. She has a boyfriend who she’s been dating now for about five months. They’re both fifteen.

Several times the two of them have talked about how they don’t want to have sex any time soon but would be fine losing their virginities together.

Unfortunately he has a bit of a habit of ‘getting caught up in the moment’ when they’re together.

She went over to his house today and for ninety minutes he tried to ‘get himself inside of her’ even though she was saying ‘no’ and ‘stop’.

He would say things like ‘don’t be such a buzzkill’ and ‘you know you want it’ and she would respond with ‘yes, but...’ and never quite finish.

She tried to walk away a few times and he would finger her in a way that he knew hurt her, or grab her boobs and butt so hard it caused her pain (which he intended).

Like I said, that went on for an hour and a half. She came home and told me about it. She said she isn’t breaking up with him, and doesn’t want me to tell anyone, and wants me to continue being friends with him, even though he’s been shitty to me before, on top of all of this.

I am a very nice person, but I have never ever been this irate at another person. I’m honestly scared that he’s going to rape her next time she goes over, which makes me want to tell our parents so they can take care of it. But she asked me not to.

I’m really stumped on what to do, or how to process this, or how to comfort my sister, who feels like it’s her fault.

I guess I just really need advice.