Pete: I think your main problem is that you were focusing on the boobs too much. They're distracting you while you do the other facial features. Try again with her in a turtleneck and I bet you do great!
This whole experiment reminds me of the Oasis art that also got ruined by the mouth. Same issue, the lips are too thick on the sides, looks like she got a bad collagen injection. It's a solid attempt though, and a lot of the rest of the piece looks good.