I guess this is female anatomy week. Good, I need the practice. Here is what I see:

The image on the left is my analysis of your original. The image on the right is the start of an edit, I didn't have time for more today.
The main problem I see is the broken neck/torso center line. The torso has a vertical line from the center of the chest to the belly. The neck is also perfectly straight, but these two lines don't meet. The result is a broken figure. The disconnect also goofs up the shoulder since it can't reasonably connect to both pieces.
Possible solutions:
1) Draw a spine and then build the forms on top of that (ribcage, then neck/shoulders), then build up the rest. This works for realistic figures, and is probably the best way to go.
2) Use a set of generic shapes as the starting point. This only really works for cartoon figures, but it can be rather quick.
Other minor crits:
The neck is too thick as well as too long (if you measure to the breastbone). In my edit I thinned the neck by a pixel and made the whole thing shorter by one pixel, and then brought the breastbone up to the base of the neck. It still looks long and thin, but it is actually shorter.
The eyes might be a pixel too low. This is more a style choice than an anatomy crit. What you've got works if the head is tilted down, but pulling the eyes and nose up a pixel gives you more room for the face.
The armpit is just a mess, but I think fixing the alignment of the spine will let you fix the shoulders and this problem will disappear.
The one upper arm is too long, and too thick.
The edit:
I only got to the face and neck. Pulled the eyes up a pixel, with minor adjustments to the cheek and hairline.
The neck was thinned by a pixel and shortened. Then I moved the whole neck/head 1 pixel the right so it lines up better with the torso centerline. It still doesn't line up smoothly, but it's better.
Further work would be to pull the breasts up one pixel, fix the shoulders. Hopefully the edit shows where there is now room for a shoulder joint (like a small round ball) which would then lead to a better arm shape.
Hope this helps,
Tourist