Brandy's parents were unemployed earthlings and took jobs as illegal migrant workers in Shi'ar territory. Her parents were separated, and her pregnant mother, Suzanne, was eventually arrested for being an illegal alien. While being transported to prison, the White Event occurred, granting the Star Brand to Suzanne, at the same time she went into labor. She used the power to escape prison and accidentally destroy a number of planets. When she finally gave birth, Suzanne died and passed the brand on to her new baby girl. The Avengers would volunteer to take custody of the baby, naming her Brandy.
Brandy was created by Jason Aaron and Ed McGuinness in Avengers (2018) #3. Aaron's Avengers missions related to years of manipulations from Mephisto related to the oldest legacy mantles on Earth, and the Star Brand was the second to last one to become active.
Major Story Arcs
The Age of Khonshu
With the last heroic mantle, the Phoenix Force, on it way to Earth, Khonshu instructed his guardian, Moon Knight, to magically take control of the 6 other mantles because Khonshu did not trust them to take on Mephisto. With new upgraded enchanted weaponry, Moon Knight was able to steal the power of 4 of them. Thus, Iron Man and Captain Marvel grabbed Brandy and went on the run.
Iron Man almost gave Brandy to Moon Knight having seen vision of what Mephisto had planned. However, he fought the temptation and trusted Brandy's well-being exclusively to Danvers. They travel to space where they think Moon Knight can't follow. At the same time, back on Earth, Moon Knight loses trust in Khonshu and drops his crusade. This forces Khonshu to use the powers of the stolen mantles to chase Brandy into space himself.
After disconnecting from Khonshu, Moon Knight is chosen by the Phoenix Force. Using the Force, he catches up to Khonshu and strips him of the mantles, allowing them to return to their previous guardians. After which, The Phoenix releases Moon Knight in search of a more permanent guardian, and The Avengers are able to return to Avengers Mountain with Brandy.
One day, Brandy awoke in an alternate reality floating in space. This new reality was caused by Agent Coulson using powers granted to him by Mephisto. He remade the world so that the Squadron Supreme were Earth's Mightiest Heroes and the Avengers never experienced the secret origins that made them superheroes. Without the Avengers, Brandy was never recovered in space.
She was found by Rocket and Groot, who raised her. Between mercenary missions, they would help Brandy train her new powers and as a result she developed an aggressive attitude not unlike Rocket's.
When Rocket was hired to kill Doctor Spectrum, Brandy was able to share her power with him when it looked like he was losing. This wasn't enough, and Spectrum killed Rocket. Brandy wanted to follow Spectrum to Earth and get her revenge. On her way, she was found by a Wakandan spaceship, which brought her to Black Panther. Soon after, Blade, who remembered the old world, showed up to Wakanda with the teammates he was able to inspire to take up the fight.
Unfortunately, Coulson and the Squadron tracked them to Wakanda. They were pretty evenly matched, but the combined power of Brandy's Starbrand and Echo's Phoenix Force were enough to disrupt Coulson's pandemonium cube (the source of power Mephisto gave him), causing it and Coulson to get pulled back to hell, returning reality to how it was.
One side effect was Brandy kept her development from the previous reality. She remained at her toddler age with a bad Rocket-like attitude and some control over her abilities.
Brandy should have access to all the powers of the Star Brand, however, given her age and lack of experience or training, it is unclear what she can do. Thus far, she has shown an ability to fly, shoot energy blasts, and survive in the void of space.