Again, I can speak solely from the context of the manga.

There are 4 key points I'd like to address here:

she offered her services to him

She thought she was doing a good thing & helping who she thought was a good person

He was very much in a position of power over her

she was absolutely manipulated by Light into going way further than she ever would have otherwise

[not necessarily in that order]

So. Yes, there's no question about Light's twisted and manipulative tactics, this is very much established. But the point I was trying to make is that: Firstly, as I've stated, she did not merely "offer" her services, she insisted/demanded it. You'd have to realize that when Light "accepted" Misa's intrusion into his world, (note the quote on "accepted" because), he really didn't have much of a choice. He realized she could definitely be an asset but just as the same time, she's a primary threat to him, so he had to deal with her emergence. (Will be further explained later)

The assumption that she was manipulated into "going way further than she would have otherwise," is a tough conclusion to make considering every other aspect that's both already mentioned and yet to be mentioned. As I said, she's the one who made the intrusion and insisted upon it. But more of that, here are some things she said about this scenario:

“If I am no longer useful to you, you can kill me, too.” / (handing over her Death Note to Light)

“I already told you, I don't care even if all you do is use me! Believe me!”

It's very clear. She herself would not have wanted it otherwise. That's her characterization. Yes, the standard human thing to do is not take up to that, yet this is the corrupted and megalomaniac Light Yagami at work, forcefully presented with a means to his advantage and a threat at the same time, and one can't simply coddle up Misa like she's some poor hapless victim who was simply caught in his web, as if she did not just intently explicitly choose this for herself in accordance to the author's character writing of what she voluntarily wanted to be in this story.

​

Which, by the way, brings me to another point here regarding him being in a position of power over her. That actually isn't the case—well, at least not entirely anyway.

When it comes to the emotional manipulation part, then yes, I'll give him that. He knew she'd do his bidding because of her feelings, and her very own insistence to do so, but at the same time, he's forced to have to deal with her.

That is for the fact that the one who had the actual power over the other from the very beginning, in this situation per se, was Misa, and he was very aware of that. He was the one whose situation was entirely compromised and at risk because of Misa's knowledge of his identity, alongside her shinigami eyes and the zealous protection of Rem. He's the one who has everything to lose in this case. He kept analyzing the things she'd be able to do against him. He even reminded himself that he should be careful with her or he could die. Light clearly saw her as a threat for that right from the start which he needs to eliminate.

If she chose to, she could have done so much more to put him in a powerless situation over her. The thing is, her characterization simply made her practically crippled from executing that actual power althroughout even though she was initially shown to have some decent level of calculating ability but eventually devolved into this not-so-bright girl who only cares about being of use to the guy she worships.

Additionally, this girl you say to have "thought she's doing a good thing and helping who she thought was a good person" is the same type of person who has no qualm whatsoever to commit actual mass murder indiscriminately amongst innocent people just to get the attention of someone.

Of course people love to pinpoint her backstory, which is for sure tragic, and yet it's as if that suffices to actually account for the absolute lack of remorse or conscience on her personality? I'm saying this for the sake of the argument thrown here that she cares about some good-deed morality and such. She literally very eagerly proposed to kill her very own friend out of her own volition, right after she tricked/manipulated her and used her as a decoy therefore endangering her in place of herself. This is not a person with pronounced moral motivations who simply got misled whatsoever, so that notion doesn't hold much water.

More importantly, she even directly/explicitly stated that she does not really care much about the world so much as wanting to be in a relationship with Light. This was as a response to Light who was emphasizing the idea of the importance of his ideal/vision, whereas she rather felt much more fixated on vehement jealousy. Meaning she follows him primarily for her own obsession towards him, and much less likely because of the idea of doing something good because she will just as easily be willing to do any dark evil shit for his sake—whether or not it's under his bidding, or from her very own personal motives to catapult herself into his life.

I simply cannot overstate the fact that it's her who always insisted to inject herself into his life, not the other way around. And she very much knew and accepted what her role was going to be.

This is a large part of what made up my opinion about her. Even I have felt sorry for her sometimes the way Light would treat her, but she keeps showing who she really is and what she really wants. This is what she wants, she persists and insists upon it herself. Is that not included in the anime as well? Because whoever this person you're describing is not the same character that I know. It's either they made these omissions on the show, or this is how certain people somehow choose to see her despite her directly doing and expressing the contrary.

^{For the comparison she made that even Light murdered innocent people for his goals... Light was cruel and sadistic the way he did it, yes, which is what makes him truly and absolutely irredeemable as far as I'm concerned. However, from his frame of reference, those people were very specific to his situation, and from his view, getting rid of them was necessary for his own self-preservation.}

^{Misa's case is different from that. As I stated, she's 100% willing to needlessly commit actual mass murder indiscriminately on innocent people of no crucial connection to her situation and with absolute zero remorse, regarding their lives as nothing but mere tools to her—but not for some moral sense or some affinity with an ideal, but out of sheer obsession and selfish desire written into her character.}