Alyssa Rosenberg has some further thoughts on the Manic Pixie Dream Girl character archetype:
He and I were talking about this a little bit a couple of days ago, and while I think it's pretty clear why MPDGs are a fantasy for men, I also think the archetype has some utility for women. After decades of makeover scenes and unrealistic physical and behavioral expectations, there's something kind of appealing about being told that the fantasy isn't the Herve Leger bandage dress and the body that goes with it, it's the quirky cardigan; that it's not about having to fix yourself, it's about someone else has to do the transformative work and all you have to do is help. I don't necessarily think it's a good trade, and I don't actually think it makes for fully fleshed-out characters or exceptionally interesting movies, but I understand why it might feel worth it.
I think this is one of the key differences between the Magic Negro and the MPDG. No one consciously wants to be the Magic Negro. But with the MPDG, you have an example of sexism manipulating women by making them internalize what is supposed to be "desireable" and being encouraged to meet those standards. It's not actually that different from airbrushed bodies on magazine covers, it just seems deeper.