Nice look, well rendered. Is that a photo background?

From what I can tell she does look a little taller than normal but she also looks a little older to me so it balances out.

I like what you did here, nice costume look and a great flying pose. Looks really good to me.

First off -- great job on the pose and great choice of background! The character really looks like she's flying.

Very nice job on the costume as well -- a bit basic, but it looks like you did a good job with what you had available.

Now, the negative side. You mention thinking that she's too tall -- no way to tell, without something to compare her height too, but she does look like she's built very thin. That's a legitimate choice, if you wanted to do that, but I'm used to seeing Mary looking a bit more... voluptuous.

Second, it looks like you left her expression at or near the default pose, which gives her a bit of a "staring off into space" look. If it were me doing it, I'd point her eyes up a bit (it just feels to me like she's climbing, from her pose), and maybe furrow her brow noticeably.

Lastly, I like her hair darker than you're showing, but that may simply be personal taste as well.

All in all, a very good job, with only minor things to quibble about!