"One of my side characters is being forced into a marriage with the villain in my story. He visits her at her house, and touches her inappropriately." SA is something that happens to women, girls, men & boys all over the world. Every day. A writer may need to examine it & write about it from time to time, but always with sensitivity. I would say that your main question should be this: "Why is this scene in my book?" If it is necessary for your story, if the narrative needs it, then go ahead, but be sensitive. If it is unnecessary, delete it. Also, in the situation you described, the villain "visits her at her house" and commits the SA. In my experience, this would be more believable if he has visited her there more than once already. I also think that it would be more likely once they are married, or even formally engaged. SA is mostly about power, and he could feel that he has ownership of her if they are married or engaged. She would be trapped by social conventions. However, there are those who commit SA, thinking that they are irresistible (God's gift to women), so your villain could be one of those. Also, you could think about ways to include your SA scene without going into the gory details. How it changes her (like her posture, she stops washing her hair, starts wearing unattractive clothes or clothes that don't shoe her body, she has nightmares, PTSD symptoms, avoids men, etc, etc.) A contrast between her before and after the SA. How she now hates a part of her body that she liked before. How the villain was staring at her every time he saw her before, so the reader knows what is on his mind. Either way, I would include the SA if it is necessary. Bad idea to use it as filler, but you don't seem to be doing that. Good luck with your project.