I'm glad you like Alya, the hate she receives is unreal. I'm guessing that you haven't been all that deep into the fandom, it's not exactly rare. If you go to AO3 and sort it by kudos, a lot of the most popular fics make Alya into a mean, awful bully (usually due in part to Lila's influence, though I've seen cases where even LILA'S shocked at how cruel and violent Alya is) who terrorizes Marinette, so that Marinette, with the help of her new best friend Chloe (and often some other love interest, like Damian Wayne, Felix, or Luka), can expose Lila's lies and Alya and the rest of the class as being useless and cruel and try to destroy their futures, and make sure that they know that all the happiness in their lives only came from Marinette's efforts, and now without her help, they're left to just wail in despair.
It's really, really bad. There are thousands of fics where Marinette goes "Alya's proven herself untrustworthy so I'm taking away her Miraculous, Chloe's going to be my main back-up instead!" Or where like, Alya's pressuring Marinette into babysitting for her without pay and behind her parents' back, so that Alya's family can be disgusted and disappointed in her actions when they find out.
Alya's not perfect, but she's constantly demonized for shit she NEVER EVEN DID. And that other characters have actually, canonically done, even!
With how ingrained it is in saltfics (btw, if you want to see more about this kind of thing, just google "saltfic", you'll find it), how many double standards are applied to Alya, and how little it has to do with what actually happened in canon, at this point I just think it's bigotry. I just block the people who participate in it, it really disgusts me.
DAMN ive been in the fandom since the show started but i have fallen off in recent years only kinda staying in my corner but this makes me very fucking sad. Alya is literally the redeeming grace of that show imo the only reason I continued to watch it for a period of time was bcuz of Alya.
Hope people come to their senses because man thats fucked up. Also replacing her with chloe ðŸ˜ðŸ˜ðŸ˜ just say ur racist and go ðŸ˜ðŸ˜