Manic Pixie Dream Girl much?

I really don't think Sophie qualifies as a manic pixie dream girl. That archetype (or trope or whatever it is) requires a needlessly quirky character whose sole purpose (or primary purpose) is to make the dreary hero loosen up and enjoy life.

Sophie isn't needlessly quirky. Her eccentricities are quite necessary for the plot. On the second part of the manic pixie dream girl, she does help Stanley be a bit less of a jerk, but she doesn't do it in the classic manic pixie way (ie: Stanley does not end the movie indulging in "quirky" behaviour). Furthermore, she does not act out of no real discernible reason. Manic pixies (as I understand them) don't really operate with any real internal character logic, helping the hero just because they do and the scriptwriter wants them to.

I don't think Sophie fulfills enough elements of the manic pixie dream girl, certainly not consistantly, to qualify her as one. I've seen Allen accused of this before with Annie Hall. I don't think Annie was a manic pixie, I don't think Sophie is, either.

Not really.

Woody Allen uses young women as muses very often in movies. Sophie, by the end of the movie, has come to inspire Stanley and will likely go on to be a "muse" of sorts to him.

If you know Allen's movies then you know this character immediately.