My sister dragged me into her divorce

UPDATE: I posted this over a week ago and I haven't read the comments since the night I posted. I didn't sit on this for over a week but I dragged my feet on following up. I was pretty overwhelmed by my sister by the time I posted and I didn't want to deal with this until I felt calmer. I didn't expect this many responses and I'm really grateful for all the advice and support. <br><br>The situation was pretty clear to most of you and I think it helped me to hear that outside perspective too. I'm going to hire a lawyer and set some clear boundaries with my sister (and her friends). I've blocked everyone from her side on social media and I'm trying to avoid my sister and her case as much as possible.<br><br>I'm not really sure what to do about my loss of trust of my sister. I don't know if I'm going to be able to fully trust her again anytime soon. I'm also leaning on my therapist to help me with this. It was really hard to hear that my sister had no problem using me to hurt her ex and it made me question her motives in general.<br><br>I appreciate the different perspectives many of you brought - about divorce, the general legal process, family dynamics, etc.<br><br>ORIGINAL:<br><br>I (26F) am a law student. My sister is going through a divorce and she wants me to testify on her behalf in her case. I don't want to and I told her so but she is threatening me and I'm not sure how to handle this.<br><br>My brother in law cheated and that's why my sister is divorcing him. She told me that she was going to drag him through the dirt and she wanted my help. I told her I didn't want to be involved but she tried convincing me for almost an hour. I told her no again and she got angry and told me I had to because she was family and I had to support her. I said no and she told me she didn't have a choice and she was going to make me.<br><br>A week later, I started getting calls from her friends asking me why I wasn't supporting my sister. They were all on her side but none of them hated my brother in law. I don't think any of them would do this but I'm taking the calls because I don't want to give them an excuse to escalate by ignoring them. <br><br>I have a mezzo voice - I've had singing training and I've sung in front of people but not professionally. My brother in law complimented my singing in front of his boss and business partners during an event we all attended. I didn't know his boss was looking for a singer until he approached me to perform for him. I've sung for him a few times and his company has paid me well.<br><br>My sister is saying that I'm sleeping with her ex husband and his boss and that's why I'm refusing to help her. Her friends are echoing this. They're all on her social media posted all over the place. None of its true and I think my sister knows it but she wants to use it to force me to help her.<br><br>The singing for her ex's boss happened way before she was divorced. My brother in law and I have always been friendly and I would have thought that was fine since they were married but now she thinks its an issue. I don't know what she's going to do but I'm scared.<br><br>How do I get out of this? I don't want to be involved in their divorce but I'm being dragged in on both sides.