For as much as I am on Alya's side in "Revelator" - and believe me, I AM - I still wanna point out that Alya and Marinette are two sides of the same coin when it came to how they eventually handled their sides of knowing the secret regarding Adrien's whole life.
Marinette: I don't wanna say the truth because it makes me uncomfortable and could result in permanently changing my perfect relationship with Adrien. So I won't fight for his justice and put myself first.
Alya: I don't wanna lie because it makes me uncomfortable and could result in me being dragged into this whole mess I hate. So I won't fight for Adrien's justice and put myself first.
Let me clarify right away that I really LIKE that the episode had Alya make a proper statement that she's not only NOT supporting Marinette in this, but also that Alya is not going to take care of Marinette's mess for her. Alya has been stuck in the Black Best Friend trope for seasons on end with her being stuck with cleaning up after Marinette, solve her interpersonal massive fuck ups (are Gang of Secrets and Hack-San ringing a bell?) and with her life getting more and more consumed by Marinette who never once actually asks first if Alya even wants all of that dumped on her because Marinette just assumes Alya will agree or at least give in for Marinette's sake "and the greater good". (Illustrhater is the current worst case of this).
I LIKE that Alya said "this is YOUR immoral mess, solve it yourself". Because, by all means, Alya HAS the right to draw this line and insist on her not just existing to solve Marinette's problems she refuses to ever face or even consider before they blow up.
I think, in concept, this is EXACTLY what Marinette needs. For one of the main people Marinette always just dumps everything on and takes eternal emotional refuge in to say "no, I'm out. Take care of this yourself".
This SHOULD be the right development for Marinette in concept because it SHOULD mean that Marinette would be narratively faced with having to finally learn to get her behaviour in check and prevent these problems from happening in the first place. A variation of this is also one of the main things Adrichat had to learn in season 4's Ladynoir conflict. That he himself has to care for his actions and needs and take care of nd realize his place in the world because Ladybug can't and won't be arsed to consider him at any point (which still hasn't actually changed yet)
That the people who used to take care of your messes or be the emotionally strong, mature, and reliable ones will and should tell you that they wont do it anymore, especially when you genuinely fucked up. That's NORMAL. And it's IMPORTANT. Because not getting to have other people to solve your problems, or at least significantly de-escalate it for you, will more often than not lead to you actually reflecting on your actions and put things in much better and braoder perspective FIRST before you do it.
I repeat, this happening is NORMAL. It's literally how you learn to live your life independently.
To finally bring this back on topic: while Alya HAS the right to draw this line and insist on not solving Marinettes mess, this also means that Alya disqualified herself from getting to say she fought for justice.
That's just how it is. Alya can't say "no I'm not doing this, I want my memories wiped away" and then get to claim she thinks Adrien's right to know the truth is the priority. Cause it wasn't.
Alya in the end put herself first and not Adrien. Alya knows that Marinette is keeping it a secret because she doesn't wanna face the difficult situation and then still tells Chat Noir that she wants her memories wiped, which means Marinette will not be held to standards by anyone again and possibly now fear anyone finding out about it even more.
It also came with the obvious risk that came true in the end: mind-wiped Alya picks up on her friends having conflicted feelings and ends up indirectly validating and supporting Marinette in her only prioritizing not facing consequences because now Marinette sees an oblivious Alya again who she prefers to have by her side.
Marinette knows Alya doesn't approve, but has no active motivation anymore forcing her to not just write that off as, for example, Alya's reaction "under bad circumstances" to instead have Alya now validate her left and right in her 'second chance'.
Alya unfortunately is indeed written to think better of Marinette than she actually proves to be and do because she lacks the full insight on what Marinette does and how she operates.
Sublimation was actually perfect set up for this. The episode starts by Marinette going stalker and at least DARK orange flag girlfriend on Adrien and Sublime and yet Alya was out here just saying "oh well, can't stop her 🤷♀️ good thing Marinette likes to learn lessons 😉"
Only for Marinette to end up hurting a disabled person and ruining a sponsorship because Marinette took all her anxiety out on Sublime. It was only thanks to ADRIEN and Marinette's Ladybug magic privilege that this disaster could be saved and solved.
No, Alya is not Marinette's babysitter. She isn't responsible for preventing Marinette's actions as if she were a toddler. But what I am saying is that she saw all the red flags and just said that Marinette gets to possibly use Sublime as her anxiety chew toy because "oh well 🤷♀️". As if Alya doesn't know that Marinette is by now used to extreme cases like akuma battles.
That's a PERSON Alya just declared a learning dummy for Marinette's behavior and that's already by itself a messed up thing to do.
Sure, Alya did so because she thought that Marinette's extreme actions and anxiety couldnt/ wouldn't hurt Sublime the way she did, but that doesn't matter. Cause Marinette DID and that was in fact predictable when you have all the context which no one ever GETS because Marinette doesn't let anyone have it.
By all means, Sublimation proves that Alya and Adrien SHOULDN'T just always give Marinette the benefit of the doubt and blindly let her do this shit or make excuses for her and even solve her problems. Because that lead to Sublime getting hurt.
Marinette is not as good and considered as other characters thinks she is and that angle is continued in Revelator.
Alya puts way too much trust in Marinette doing the right thing after being given a full-blown out, and Adrien as Chat Noir also shouldn't have prioritized again that Ladybug's lips stop trembling because she's faced with something unpleasant. Already in Sublimation Chat dismissed the akuma victim to excuse Ladybug without caring much for what she even did.
Now again in Revelator, Adrien sees Ladybug being in a situation she isn't comfortable with and prioritizes thinking of a way to get her an out instead of caring what he's being used to cover up.
That's the wrong thing to do. For both Adrien and Alya. But this makes Alya's decision even more anti-justice because she SEES that Chat Noir doesn't know what's actually happening and that he's for now instinctively helping Marinette to cover everything up, when earlier Marinette told her that she doesn't trust Chat Noir with the truth because she thinks he would hate that lie just as much as Alya does.
Alya has every red flag in front of her and still decided to insist on her right to not having to take care of this.
And again, she gets to do this by principle of her being an individual, but you can't call it justice. You cant even really call it fair because of how Alya is dismissing Adrien and Chat Noir in this.
But what I will call it, is Alya and Marinette being the two sides of the same coin. For good and for worse.