After the first episode of She-Hulk, quite a few things were cleared up. Bruce used She-Hulk’s unique blood to heal his arm fully. And by now, you would have made out who exactly did Captain America lose his virginity to. But another major revelation from the episode was that, unlike Smart Hulk, She-Hulk did not have an alter ego. So, people were left asking why She-Hulk does not have a split personality like the Hulk.
Both Banner and Hulk have had to fight to stay in control. Most of the time, Banner was in the driver’s seat. But there were times when Hulk took control. And these two have had to switch back and forth constantly. Banner was baffled that his cousin Jennifer had no alter ego and was always in control as She-Hulk. Banner had to figure things out with the Hulk. And he spent 18 months in his gamma lab mixing his two personalities. So seeing his cousin Jen having total control in her Hulk form would have made him jealous.
He made a whole binder on how to be a Hulk. But all those records of his experiences… all the dos and don’ts, went down the drain. Still, people have been left asking why She-Hulk is so different from the Hulk. And why she doesn’t have an Alter-Ego. Well, the answer is actually more specific to Hulk and not She-Hulk. You see, in the comics, Bruce Banner had a very traumatic childhood. His father was an alcoholic, and he was abusive toward Bruce. This wretched guy also killed Bruce’s mother, who loved him very much. So, Bruce’s trauma created a separate personality in his mind.
Moon Knight clearly showed us how a split personality disorder manifests at a very young age. Marc Spector’s mother was very abusive towards him. So, to cope with the stress, his mind created the alternate personality of Steven Grant to send him to a happy place. And at some point in time, it also created the persona of Jake Lockley to project his anger. Similarly, all of Bruce Banner’s anger and rage towards his father was bottled up in the corner of his brain. And it took a physical form when he was exposed to Gamma radiation.
So you see, Bruce always had a split personality disorder, but it only manifested during his Gamma accident. The radiation unleashed his angry persona, which turned into the Hulk. This could be the case in the MCU as well. But this is the main reason why people like Jennifer Walters and Emil Blonsky are different from Bruce. They maintain their consciences even in their Hulk forms. Jen did not have a traumatic childhood. So she doesn’t have an alternate persona.
Bruce’s gamma-infused blood entered her body when he was in control. And her blood also synthesizes Gamma much better than Bruce’s blood. So, she was never going to explode with anger. She is always in control and can keep her anger in check due to her daily routine. Being a female lawyer, she has to deal with stressful situations. And she can keep her calm even during the several mansplaining sessions she has to go through. So, she is pretty used to keeping herself in check. That’s why she also got the hang of being She-Hulk pretty soon. Yes, Anger and Fear do trigger her transformation. But unlike her cousin, she can control her rage due to her daily practice.