I'd like to counter a few things here.
Everytime she asked for help, the people she trusted ended up yelling at her face and saying "NO" instead of giving her a solution.
I'm assuming you're not talking about Nathalie, Felix, or Kagami, since they're all either actively helping her lie, or complicit in the lies via not telling Adrien the truth. Or Alix, who pretty much just told her that there were pros and cons to the truth and lies, but the most important thing was to take responsibility for her choices. So I'm guessing you're talking about Alya and Luka here.
Marinette never went to Alya for help with dealing with the "Gabriel was Monarch" thing. Alya found out about it during a fight and confronted her about it.
Rena Rouge: I thought we were no longer keeping secrets from each other. (A Tram passes by, concealing them) Mirage!
(The Mirage creates a fake Ladybug and Rena. Rena grabs Ladybug and jumps away. The tram passes and the illusions go and assist in the fight) Scene: Rooftops of Paris. Rena Rouge stands in front of Ladybug holding the orb in her hand. Ladybug stands there ashamed.
Rena Rouge: Does Cat Noir know that Gabriel Agreste was Monarch?
Ladybug: I don't know who Cat Noir is beneath the mask. What if he knows Adrien and tells him the truth?
Rena Rouge: But why lie to Adrien?! (shoves the orb back at Ladybug)
Ladybug: Because the truth is too harsh.
Rena Rouge: You don't get to decide what Adrien should or shouldn't know. Neither do I. Truth is essential for someone's personal growth, and now that I know I'm gonna have to lie! And you know I don't. like. Lying!
Ladybug: That's why I didn't want to tell you...
Marinette didn't ask for a solution. I suppose you can say that Alya gave her one anyway, in the form of pushing her to tell the truth (at least to Adrien), but she doesn't want to do that one.
Now, Marinette DID actually go to Luka for help. And he DID try to give a solution. Bit since he didn't fully explain it and just asked Marinette to trust him (likely because it has something to do with Adrien being Chat Noir), Marinette backed out and erased his memory.
Luka: Marinette, tell me what's going on.
Viperbug: Luka, I... lied to the entire world. Adrien's father wasn't a hero. He was Monarch. He made me swear that I wouldn't say a thing so that Adrien would think well of him, in order to protect him, but now because of that I'm having to lie to everyone!
Luka: Why did you do that?!
Viperbug: Because I love Adrien more than anything, and he'd be in so much pain if he'd ever have found out! He could get akumatized by the new holder of the Butterfly Miraculous. And I'll never, ever, EVER let anyone hurt him! I have to keep this promise and hide the truth from him, even if it burns my lips and my heart every day until the end of time. Do you think I did the right thing?
Luka: I don't know, Marinette, I... I'm going to ask you something that you'll probably find very strange but... please let me borrow your miraculous.
Viperbug: What? Why?!
Luka: I know things that you don't, and I'm probably the only one who can fix this. Give me your earrings!
Viperbug: No, no! Tell me what you're going to do, and I'll take care of it myself!
Luka: Marinette, I love you! You're the strongest person I've ever met but this time I'm the one who needs to protect you! (He grabs her wrist.) You have to trust me!
(Viperbug pulls away from him.)
Viperbug: I'm sorry, I never should've told you any of this!
So I don't think it's fair to say that Alya and Luka just yelled "NO" at her when she went to them for help and didn't give her a solution. That is factually not what happened.
I do know that Marinette's traumatized by watching Gabriel die in front of her, even if it was non-graphically, and needing to deal with the fact that he's gone forever. I don't really believe that she would have sacrificed her own life - if she was genuinely deadset on that, she could've started on it before Nathalie even showed up, she still had both Miraculous after all. But I can see why she thought she'd at least consider it. I don't think Felix and Kagami had anything to do with it though, there's not much hint of that.
Meanwhile, yes, Adrien can enjoy the memories of his father but Gabriel by the end of his life wasn't that man anymore. And that didn't start with Ladybug and Chat Noir, not with Marinette, that went YEARS beforehand. And the only one who can figure that out is Adrien himself.
The problem is, Marinette gaslighting (well, a lot of people gaslighting, but Marinette's leading the effort) Adrien into trying to believe that Gabriel was actually a good, altruistic person is actively hindering this effort. It's not just stuff directly linked to the lie, she was trying to rewrite what Amelie was saying mid-interview to paint Gabriel as being a nicer, better person overall. Adrien's actively been trying to figure out how Gabriel became so cold and come to terms with the man his father's become, but he can't do that when all he's hearing is that he's been wrong about what his father's like all along. I don't know how Adrien's meant to internalize and come to terms with all the issues with his father when Marinette, Nathalie, and anyone they can recruit, keep telling him he was actually a wonderful person and everything he did was actually for Adrien's own good.
Note: I'm not using gaslighting to just mean "lying". I'm using gaslighting because the lies that Marinette's telling Adrien about Gabriel, and trying to get everyone else to tell about Gabriel, are meant to rewrite his view of his father to be more positive overall so that he accepts the "Gabriel is a hero" lie and stops digging into it.
It's so easy for everyone else to say "tell the truth, punish the villain" and you forget about the victims. Because that's why Alya fails in her argument: she just wants the truth out without thinking in the consequences for everybody else. Kagami losing her mom, Félix losing his freedom again, Adrien being shamed and his custody taken away. The victims are more important and now Marinette is part of them too.
This is inaccurate, Alya never pushes for this. She's specifically pushing for ADRIEN to know the truth. She never tries to push for the general public to be made aware of everything. None of this applies to just telling Adrien, which is what she actually pushes for.
While I agree with your statement that any plan to deal with the villain should also weigh the effects of that plan on the villain's victims, I factually disagree with a lot of the assertions you're making to support that conclusion.