A couple of my thoughts on the subject:
1) If I intend to study changes in the shape of most anything, (eg, the subject's face), I want to be able to concentrate on the shape independently of any intense colors or lighting oddities (eg, unintended shadows) that might be present. So to me, this says, "let's look at the changes in shape in a B&W version of the image, and try to minimize the shadow across her (viewer's) left cheek".
2) Deciding on the "best" new shape of someone's face is probably one of the most subjective artistic decisions that a photoshopper can make. I have never seen this model in person, so I have no idea what she "really" looks like; I have no idea how much of a change she and the photographer will accept; and, I realize that my perception of what is an "improvement" in the shape may be exactly the opposite of what other people might prefer, and such preferences vary from culture to culture and age group to age group. Also, people who know the subject will usually accept only relatively small changes to the shape of someone's face (...eek! It doesn't look like her...), whereas much larger changes will usually be acceptable to people who don't personally know the subject and might be thinking more in terms of cultural norms, cultural stereotypes of beauty, not this one individual.
However, in spite of all of the above considerations, IMHO, one always should have a clear, well-considered goal in mind before playing with the liquify or any of the warp tools. So, FWIW, my goal was a less elongated shape, whereas it's pretty clear that the goal of the OP was a more slender face.
3) I find it much easier to compare efx if the pix are shown sequentially, one-after-the-other, rather than side-by-side.
So,
George Belmont , with respect to your request for us to judge your liquifying work, I certainly don't see any technical problems with what you have done, but some people (like crazy old me, LOL) would aim in a somewhat different direction (if given the liberty to do so). Anyway, see what you think about this quick and dirty alternative treatment. In the 3 frame GIF animation, it should be pretty easy to pick out which is your original, which is your tweaked version, and which is mine (all reduced to B&W).
Tom M