I've never experienced suicidal thoughts, so I can't be certain, but when I read stories like this which are basically aimed at telling suicidal people that they have reasons to live, it feels like it would just come across as patronizing and preachy. I genuinely believe that someone could theoretically be emotionally and mentally stable and still decide to commit suicide (I'm not sure why fe would want to, but that would be feir choice). However, the situation this manga portrays is not that. Misao wants to kill femself because fe's unable to cope with feir regrets and trauma from the past, so in that situation trying to help fem come to terms with it and cope as Maria does is probably the best course of action. But in feir attempts to cheer fem up, fe minimizes feir responsibility. Fe says "It's not your fault I ended up like this," but...the thing is...it kind of is feir fault. Now, obviously, Misao's not responsible for Maria's actions. But fe is responsible for suggesting feir actions as well as encouraging and even pressuring fem into taking those actions (fe knew fe wanted to play with them, so fe should have known that fe would've felt incentive to do what it took to do so). People have to learn how to cope with their guilt, but the way to cope is not by glossing over your mistakes and acting as though you weren't responsible when you were. So in that sense, I feel that this manga has a shallow and badly considered emotional resolution, which could potentially instill unhealthy coping skills in the readers.
Also, it has to be mentioned that Maria is a hypocrite. And feir entire pro-living message just goes up in smoke at the end.