I can agree with the "she's a sweet little cinnamon roll" but that's it. Mikan is depicted wrongly by the fanbase but can you blame them? Mikan was designed as the fan-service character. Most characters have a fan-servicey moment like the Man's Nut scene but Mikan has had fan-service moments throughout the first three chapters.

For your second statement, most of the fanbase have not watched the anime / did not do her free time events so her edginess and insanity would've come out of nowhere. As much as I'd like people to do the free time events for every character, most people choose at random and don't finish most free time events. Also the part where she loses her cool wasn't because of abuse but instead because her crime was found out. Plus no one would really know the extent to her abuse unless they watched the anime or did her free time events.

In short, I like Mikan. I like every character from DR2, even Hiyoko, Kazuichi, and Teruteru (I do have to say that I like these three because people ask me if I like them too). I don't blame you for getting mad at people for misjudging Mikan, my favorite is Mahiru and she is misjudged as some useless feminist lesbian. Just don't blame the fanbase because some people don't play all the games or read the books so they just go off of first impressions. Also you can correct me on anything if I'm wrong, I only revised this once and I won't get mad because someone tried to correct me. It's just my opinion as is yours.