The Hulk's wife Betty Ross turned herself into the Ultimate She-Hulk to prove Iron Man wrong. Frustrated that Nick Fury tapped Wolverine to track and kill her ex-boyfriend, SHIELD's Public Relations Officer vented her frustrations to the Ultimates. Interrupting a friendly match between Captain America and Iron Man, Tony Stark's answer helped motivate her to steal the illegal serum that turned her into the She-Hulk who would interrupt Hulk and Wolverine's ongoing battle.
Betty Ross is the long-suffering romantic partner of Bruce Banner, her life in a state of constant upheaval due to the Hulk and the influence he's had on her life. In the Ultimate universe, a separate Marvel world outside of mainstream continuity, Betty is the Director of Communications for SHIELD and ex-girlfriend of Bruce Banner. Bruce’s obsession with Betty and her behavior towards him was one of the primary motivations for his return as the Hulk whose rampage almost destroyed Manhattan and killed hundreds. Although he secretly remained in a special cell in the Triskelion, Bruce’s true identity was revealed in Ultimates 2 and he was executed by SHIELD courtesy of a nuclear bomb for his crimes. In Ultimate Wolverine vs. Hulk, SHIELD discovers that Hulk survived and so Nick Fury taps X-Men’s Wolverine to track and kill the Hulk to prevent this from going public.
In Ultimate Wolverine vs Hulk #4 by Damon Lindelof and Lenil Yu, Betty makes it clear that she is not happy with Fury’s orders much less that she was not told that Bruce was still alive. Betty interrupts a ping pong match between Captain America and Iron Man to vent, accusing them of withholding the information from her. While both members of the Ultimates act like they didn't know, the issue is eventually met with jokes, especially from Tony Stark. Tony tells the annoyed Betty not to worry for the matter is something beyond her understanding, that she has "no idea what it means to wield tremendous power” and that Bruce should be taken care of by people who do.
This conflicted version of Betty Ross shows her cold, calculating professional demeanor hiding her emotional insecurity and guilt. Betty blames herself for her role in Bruce’s current state, that perhaps if she had treated him better, he might have not felt as compelled to take the modified serum that fateful night. Her emotional connection to Bruce makes her feel like he’s her responsibility and that he should be brought in by someone who cares instead of a hunter looking for his next thrill, like Wolverine. Whether it was out of love or responsibility, Betty steals a modified version of the Hulk serum and tricks SHIELD into flying her near Hulk and Wolverine’s battle in Tibet where she transforms for the first time. Upon her transformation, she tells the shocked SHIELD guards trying to bring her in to tell Tony Stark that she understands now what he meant about true power.
Although this wouldn’t be the first time someone tried to outdo Stark and lived to regret it, this was less about proving Tony wrong but more about Betty entering the fight instead of always observing on the sidelines. Despite her power and maintained intelligence, Betty’s inexperience causes her to get injured in a fight later with Wolverine and she is later revealed to be in SHIELD’s custody, attempting to cure her and use her as a bargaining chip to control both Bruce and the Hulk. Although its unclear how this plays into her later role in the Liberators attack on New York in Ultimates 2, hopefully, Betty’s actions remind Iron Man to be careful about what you say and to whom, especially when it comes to the Hulk and his allies in any universe.