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.
Pamela Isley's origin story is quite interesting. She was a botanist. Her transformation began due to her experiments with plants. She became Poison Ivy as a result of being exposed to various toxins and plant - based substances during her research. This led to her developing a connection with plants and a new set of abilities related to them.
One key element is the unethical experiments she was part of. Also, the exposure to toxins and plant - based substances during her work as a botanist are crucial to her origin story.
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.