Also, there's a misconception about Nana and how unfortunate girls like her are to come from a small agency or whatever.
If not for CEO Kim Kyu-sang, Nana wouldn't be an idol today. Not because he's the one who took her in after she got rejected by bigger agencies. She never auditioned for any agency. She didn't consider becoming an idol. It is CEO Kim Kyu-sang who spotted her at a dance contest and convinced her to join the group he wanted to build. His agency didn't even exist yet.
Later she met an SM scout who offered her to join the company; but she declined as she'd rather remain loyal to the one who placed his faith in her and who she trusted could debut her successfully.
So no, not all idols from nugu agencies have a sob story. I think she's the kind of girl who, if her career had to end tomorrow, would miss the thing but wouldn't be too depressed about it. She just enjoys the moment and have fun with the opportunities she gets.
Interesting fact. This also gets rid of the "big 4 criteria is very strict and other agency didn't think she was good enough" arguement