My cousin made huge lie and put me in a very tough situation

My cousin has put me in a very tough situation and I really don't know what to do. She is 17 and there is a big investigation going on at her father's house because of she came forward about her step brother who just turned 18 raping her. Me and my cousin are pretty close so I've been there for her and the family has been behind her. Her step mom denies everything and said my cousin is lying and me and her step mom actually got into it.

My cousin drove to my house last night to talk to me. She was crying and said we need to talk and she needs to someone to talk to. She's like my sister so I said okay and she tells me she lied about what her step brother did to her. I was hoping this was a terrible joke, but it wasn't. She said her mom told her too. I said to her "You're going to be an adult in 8 months. What are you going to do when you mess up and you're old enough to be tried as an adult. Say mommy told me to? How well do you think that will hold up in court." A lot of you may think I'm being a fucking bitch, but here's the deal. I'm not a fucking coddle. I'm not gonna coddle an almost adult for a mistake like this. I'm gonna keep it real. She needs to know the gravity of the situation, not be hugged and told it's gonna be OK. Thats the type of person I am. I keep it real and that's what she needs to hear. She goes on crying saying she didn't know it would go this far. This is when I really lay out the facts because she's B.Sing rn. I know my cousin. I also know her 2 types of crying. Her actually crying and then there's her "I know I'm in trouble and I'm trying to get pitty to be in less trouble" type of crying. You don't know my cousin. I do. And this was the second type of crying. I told her straight up she put me in a very bad situation and that she knew full and well how this could go. She stops crying and asks what should she do. I told her to give me time to think about how to go about it. I also told her "Don't think you can walk out of this with no consequences because this could end with some severe consequences." I let her know, her moms gonna get in a lot of trouble, she's gonna get in a lot of trouble. This lie will not go away from her step brothers reputation. I'll be surprised of her step mom decides to stay married to her father after this. She wants to figure out a way to get out of this without getting in trouble and I'm real with her. I'm telling her she's gonna get in some type of trouble. I promise I'm not a huge bitch, but she needs someone to be real with her. Now I'm in this situation and she's pretty much pushed it on me to work out for her. I dont know what to do honestly. This is a very fucked up situation that is gonna get very messy.