Harry Potter: Genderbent Petunia, but Transmigrated

[Snape CP. Out-of-character behavior may occur, so please skip if you dislike that. The romance develops very slowly, and GGAD is included.] After mocking young Snape, I got hit in the head by his magical outburst and recovered memories of my previous life. As a silver lining, I gained a System. The good news: I got a golden finger. The bad news: it isn’t very smart. It only has a learning function. The good news: it rewards me with magic. The bad news: it only rewards me with magic. From today onward, I’ll study hard and become a true wizard. The good news: I got into Hogwarts. The bad news: it’s Slytherin. I studied like crazy in first year, got dragged into the GGAD era in second year, and let’s not talk about third year. The more I say, the more I cry.