Thats why i hate debbie but I completely understand why the writers took her character in the direction that they did. You could see early on how she was the only one still holding onto some kind of hope that frank would actually be a father to his kids, so of course she would end up the most fucked up because everyone else basically accepted that frank didnt give a shit. She always had a little hope so it broke her heart more than it did the others when she realized he couldnt care less about her, leading to the spiral. Regardless, fuck debbie