After Voldemort overthrows the Ministry in DH and has the Imperiused Thicknesse installed as his puppet Minister, the Death Eaters discover the Ministry’s big secret and decide to leak it to the entire British magical populace, making them all remember the previous wars in the process.
After the end of the Second Wizarding War, Harry visited St. Mungo’s to meet with some magical scientists who were really curious to study and learn more about the effects being half killed by the Killing Curse and temporarily sent to limbo had on Harry. After performing a bunch of tests, they determined that in addition to eliminating the Horcrux, the Killing Curse would have eliminated any other kind of enchantment or spell that had been placed on Harry against his will, and publish that and all their other discoveries in the Daily Prophet.
At the same time, Harry had lost his feelings for Ginny ever since the Battle of Hogwarts and never felt any attraction to anymore, and couldn’t figure out why. After the scientists publish their discovery, Harry and his friends, as well as most British witches and wizards paying attention to them, conclude that Ginny must’ve used a love potion on him with its effects being undone by the Killing Curse. Upon this revelation, Harry immediately breaks up with Ginny and he and his friends coming to hate her, with Ginny being expelled from Hogwarts by McGonagall, kicked out of her family by Molly and Arthur, and turned into an ostracized and hated figure in the magical community.
However, Ginny never really used a love potion on Harry. What actually happened is that Harry’s scar Horcrux is what caused his attraction to Ginny, as the fact that Ginny had also been possessed by Voldemort’s soul led to Harry feeling some kind of magical connection to her that happened to manifest as romance, leading him to lose his feelings for her when the scar Horcrux’s death caused said connection to disappear.
Ginny, having been horribly hurt and depressed from all the hate she’s been getting, is desperate to prove her innocence and make up with her family and the trio. One day she’s had enough and sets out to find a way to prove it was always the Horcrux and she never would do anything like use a love potions on someone, and only time will tell if she will succeed.