While it's not up to you to decide if they should divorce or not, there are times when I do think it is ok to voice concern. Like if your dad or mom has been treating the other parent very badly, it's certainly ok to express your concern for them. But that is different then telling your mom you are mad at her for not getting divorced. Again tho, circumstances play a role. My dad use to beat my sisters and I. One day we did ask her why she didn't divorce him, and we talked about it with her, it actually helped heal our relationship. I think that should be reserved for serious issues like abuse tho, which you did mention. My sisters and I needed some answers as to why we were not protected. My mom told us why, we felt less confused, and moved on in our relationship with her.

Your mom might never get you the way you want her to. When she tells you to smile when you are talking to her about depression. Lots of people don't know how to offer the kind of support the person needs. Communication is important tho, I don't think you want resentment to come between your mom and you. Could you talk with her about what kind of support you need from her when you are depressed without making her feel defensive?