Hello there. I dig the animation. You asked for some feedback, so here I am. I'll do my best.
1. My first impression was that while the drawings were quite well, it wasn't on par with what I'm used to from you. Though I'm very aware this is likely a software issue and not a raw skill thing.
Did you use flash for this? Because I'd experiment with animation software with better drawing tools before that program. Flash is very clunky.
2. It was already said before but the white backgrounds were somewhat distracting. However what wasn't really touched on was why that was the case.
I really tried to force myself to figure out what didn't click. I googled 'bright and bleak sky' and scrolled through the examples. What I noticed was that the images with the same/similar greyish hue for the sky had much darker landscapes and objects than in your animation.
I believe the problem might actually not lie in the sky's hue, but in the brighter colors you draw everything else in. They don't match.
I also think you needed less blank space in some of the scenes.
3. I think the lack of shading really throws it off. It compounds the sky issue even more that there is no clear source of light.
4. From a storytelling perspective excessive detail is never really a good thing. And there are a good chunk of unnecessary details. I also feel like there's too much happening without making clear sense of it all.
-4a: Why is her mouth sewn shut? It isn't touched on in any way. And it isn't relevant to the plot or animation. You don't need symbolism to portray a mute character.
-4b: Having the bobby pin dissolve when she tries to (pick the lock?) is perfectly fine. You do not need to explain every detail. What was no-so-good was that I had to rewind the scene several times to figure out exactly what was happening. This could be remedied by making the bobby pin the focus of a very brief melting scene. I'd also make the melting sequence slightly longer than the one you used.
For example, keep the scene, but zoom in drastically on the bobby pin while it is melting. Have it melting slowly while moving closer to the left side of the screen. And then have the scene return to the person looking sad.
4c: Why does she collect all those little keys and doodads? Does she not know how to open the lock on her neck? If so, then why does she pool everything together instead of trying to open the lock each time she finds something?
How does she eat? Why isn't there a tube or something in her neck that implies she eats that way?
Is something sewn inside of her mouth that is causing the melting? If so, why isn't it implied via the artwork that something is inside?
I'm a stickler for these tiny little details. And people like me notice them.
5. Sound effects would have livened it up a bit.I noticed a lack of sound in a lot of different places. While the tiny robot was scanning the person for example.