2 weeks ago, it was her graduation ceremony and my parents really ruined it for her. Like they were trying to get her to tell them about all her friends, kept trying to make her do things she didn't want to, and put her through a lot of stress. It was really a hellish day, cuz on top of that, they kept saying that she was "acting" and faking her tears and everything. But she was actually really sad. Then today, it was her prom. I went with my dad to pick her up once it was done, but we couldn't find her anywhere no matter how much we called or texted her. Later on though, we found her. Apparently she went out for a walk with the guy who asked her out for prom. My dad got really mad. And by the way, I still don't actually know where she went or what she did cuz she won't tell me either. So anyway, I then overheard my dad talking with my mom about it and my dad was calling her by the most disgusting names and talking about her really badly. It really bothered me.
So, back to the original question, what can I do so that my parents stop acting this way and be somewhat proud of my sister? Cuz it's really ruining everything for her. Even though she's sometimes a drama queen, I know that what my parents are doing is really affecting her in a bad way. I wanna know what other ways there are to solve this problem other than getting therapy or something.