Well, it all started with Bruce Banner. He was a brilliant scientist. He was involved in gamma radiation research. One fateful day, there was an accident during a test. The gamma radiation he was exposed to altered his DNA. As a result, his body now has this dual nature. When his emotions, especially anger, reach a certain level, he morphs into the Hulk. The Hulk is like a primal force, with superhuman strength, and he's not really in control like Banner is in his normal state.
She-Hulk became a Hulk because of a special circumstance involving a blood transfusion from Bruce Banner. This caused her body to react and gain the Hulk-like abilities. It's a unique origin story that sets her apart in the comic universe.
She-Hulk gets her powers through a blood transfusion from her cousin, the Hulk. This transfer of gamma-irradiated blood gives her the ability to transform into She-Hulk.
It happened through a combination of events and character development. Hulk started to gain more control over his emotions and powers, which led to the transformation into Professor Hulk.
She-Hulk's powers are often more controlled and less raw than Hulk's. Hulk's strength is typically overwhelming, while She-Hulk has a better handle on her abilities.