I don't mean idiot in a bad term here. She is a sympathic idiot. She do stupid things but that purely because she thought she will be happy. She is very naïve.
Is she even naïve though? Like think of it like this for a second. Everyone in your life tells you that in order to be happy and to belong in society you've got to... I don't know, basically only watch live action stuff for your media. A weird and very different topic in terms of severity, but hopefully a bunch of people who read yuri manga can relate. They can acknowledge in a de facto manor however, that as a kid you might not just like live action media, you like animated media too, sometimes you only really watch animated media. When you grow up though, you've got to grow up, which means no more of that stuff only live action from here on out. You look around too and some of your peers haven't seen an animated piece of media since they were 13, some proudly boasting and loving some recent live action movie released. You might still like animated media, but part of you is going to be saying "Well. I'm an adult now. All of those other adults seem to be able to ignore animated stuff. Some love those live action films too, so I've got to be like them or else I can't even talk to them and belong." And that last thing might especially sting, we're generally social creatures and crave some sense of belonging after all, god forbid you have a deeper psychological need for it because of whatever reason. So eventually, after giving up animated stuff (that you still liked and still think of) and being unable to find something for so long to even talk about with your peers well into your adulthood, you find something that at least resonates with you to get you watching it. The issue is, it's not good even if you're invested, but on top of youe own feelings everyone else is talking about how it's a good show/movie so you nod your head and smile slowly letting yourself become further invested in it even if you really don't like it because you want to belong. Of course there's also an animated show that lights you up, its fun, interesting, you actually really enjoy it, but you can never talk about it, god forbid it get you alienated from your peers. Are you really naïve because you just stomach media you don't really like for the sake of maybe this being happiness that everyone else has or the notion that you'll be happy like everyone else one day or at you just a sad part of a society wide issue?
The analogy doesn't hold up perfectly of course, media can't abuse you. It can't dig its hold into you and hold you there with unbalanced power dynamics. Midori is just a sad victim of both personal abuse and societal wide compulsory heterosexuality. Hell for all she knew Maki was going to be like she was, wanting to move on and belong in a difficult world. It didn't have any malice because Maki was going to grow up like she was growing up and forget all about this love that's not really accepted but quietly allowed in the youth of girls in Midori's head. It's why she was so fine with reliving them in chapter 1, I imagine. It's all just reminiscing about silly stuff they did while kids. It's a tragedy of societal wide compulsory heterosexuality and that just seems clear as day to me. Not naivety, but a sad reality for so many women and it's why I like this series a lot.