The hag's plan was to appear at MC's and Miru's livestream, steal her smartphone, disclose the girl's real name, and tell everyone about her father's hit-and-run from about 10 years ago (or 5?), which killed 8 people, in hopes of tarnishing her reputation and forcing MC to stop the collaboration.
MC realized that the reason behind Miru's recklessness was her wanting to compensate the families of the deceased, especially when popularity was fleeting. The chat also sympathised with the girl, and one user claiming to be such a relative confirmed that they were getting money from her, and wished for her to live her own life.
Hag went on to end the livestream, summoned 3 dudes to kill the two off.
That's when she said that the reason behind his dad's murder was because he learned a secret - that they made a powerful monster as a test subject.
With that failing, she summoned dragons, which were also defeated. Then she summoned the test subject, which had a powerful barrier, and the sheer power that could affect outside world. At that point, Miru managed to start an audio-only livestream. The two tried to fight, but it was useless.
The ex-bully was listening to the livestream and decided to join MC in fighting against his mother as an attempt at atonement, even if it cost his life. Distro (the one, who warned about Yayoi) also decided to join.
After the ex-bully joined, the hag was rattled upon seeing him slip from her control. When she learned that the livestream resumed and she was being blasted online, with no way of keeping it under wraps, she started summoning monsters of all kinds. The four made a quick plan, and put it into action.
Thanks to the ex-bully, who destroyed the barrier (but not before getting very badly injured due to having worse equipment), MC could wipe out the monsters.
After the fight, there was a short exchange, then the police, reporters, and streamers arrived. She was arrested and interrogated.
The direct aftermath was Miru's reputation not only being unscathed, but improving.
The hag ended with hers completely destroyed.
The reception of ex-bully's actions during the fight was mixed, with some believing he did it just to restore his reputation. Unlike before, when he would cower in fear, he was taking the jeers in stride.