Really lovely work here. I like the pose and the photograph in general alot. In your pixel representation, the bottom of the collar, where you've drawn the line isn't accurate to the photo. One of the problems with photo references is understanding that there are no lines, and here, the way you've drawn it, there are lines, and it makes the face look larger than it is. Define your drawing with big spots of tone, especially around the bottom of the face and the side towards the scarf. You've made her look plumper than she is by using borders and light tone. Your lips, as well, don't have the feminine curves the original does.
And honestly, in your version and in Helm's version, I think the color choice has sapped the life from her- the vibrant oranges, reds, and yellows, and pinks in harmony are alot more interesting. And Helm is right about the value, you're gonna need to hit those darks alot harder.
Lovin' it, you're getting better and better. I came back to this stuff just so I could comment on this one piece.