GMC is very important in romance novels. It gives the story structure. Goals make the characters seem purposeful, like a character aiming to re - kindle an old love. Motivations add depth, say a character is motivated by past regrets. And conflict creates drama, like when family disapproves of a relationship.
In romance novels, 'GMC' could potentially stand for 'Goal, Motivation, and Conflict'. The goal is what the character wants to achieve, like finding true love or getting married. The motivation is the reason behind that goal, perhaps loneliness or a desire for a family. The conflict is what stands in the way of achieving the goal, such as a rival for the love interest or personal insecurities.
I don't have enough information to say for sure. It could be fiction, or it could have roots in reality that have been adapted or exaggerated for a particular purpose.
The story of Anger Sierra might focus on Sierra's battles with her own anger, how it shapes her personality and the challenges she faces because of it. It could also involve her growth and transformation in dealing with this emotion.
I don't believe it's true. Most of the time, when a story has a name like that, it's made up to capture our interest and take us on a fictional journey rather than being rooted in reality.