Am I wrong here

So a little back story. My sister is 16 and I’m 18 I just started in Rio Hondo college but that college gives the option for high school students to take a class in the summer. So my sister and I took ASL together. She has ADHD so I tried hard to help her because she was struggling and it was a college class. So throughout the class she wasn’t paying attention and over time I got so sick of her using me but I kept helping her. On the one quiz I took with her (we take them at home online) I got a bad grade but every other one I got a good grade. So for the final I took it by myself I really struggled and didn’t get the best grade by no fault of her own so I told her to really study hard so she wouldn’t get a bad grade to of course she didn’t and she got a worse grade then me. Part of the final is a video portion I spent two hours getting it perfect and I think I did pretty good. My sister on the other hand spent 30 minutes then asked me to look at it I told her that I would if she didn’t get mad when I was honest she said she wouldn’t I watched it and of course it was terrible the signs where way off and it wasn’t smooth like he wanted it to be. So she asked me if I could stand behind the camera and do it for her and she would copy I told her no that I wasn’t going to help her cheat and she got pissed started screaming that I never help her part of me feels bad but am I really in the wrong here I’m not sure. Please help me!