I was pleasantly surprised by this tune. Really well done. Good arrangement, great sounds, and all-around pleasing.
Sounds like her voice could use a bit more mids in her tone. This is probably because of the sibilance issue. Tone-down the sibilance, and it'd work nicely to fatten up her vocals.
Drums sound nice, but they're a bit too "mono"-ish for my taste. I'd widen up just a bit. Great playing, by the way.
For the rest, I'm not entirely sure what's going on, but it seems like the piece is a bit disjointed throughout. I'm not sure what's causing me to feel that way, either. The drums are tight, as well as the other instruments. No nits there.. So... I'm not entirely sure what's making this song seem "un-gelled" to me. I wish I could be more specific, but bottom line is this:
The song rocks, but somehow the mix is making the song and / or instruments seem disjointed. I hope that helps.... ugh, I hate it when I can't explain myself better.