This Spider-Girl’s origins are a mystery as the story she appears in involves tons of time travel that loops back in on itself thanks to the confusing actions of Kang the Conqueror. The Avengers end up getting sucked into the plot and end up in an alternate future where Kang is fighting Ultron for control of the world. Each time Kang loses, he sucks in more heroes to fight in his army to defeat Ultron, and goes back to the start of the battle and tries again.
We see this Spider-Girl as part of that army fighting Ultron, and Spider-Woman assumes that maybe she’s her daughter from another reality. We don’t get her name or anything, and at the end of the story when Ultron is finally defeated, an alternate version of Kang, named Immortus, shows up and kills several heroes, including Spider-Girl, Hulk, and Iron Man.
Positively Jim 