Whew. Out of the female subjects that I know, this is their most hated thing that happens in photos.
In the future: As a photographer, you have to be mindful of this. As soon as you see that photo on the LCD you think "oh boy, she's going to hate this one," you delete it without saying anything, make some posing adjustments, and take a different one. For posing help, search on Youtube for Peter Hurley's "It's all about the jaw" video. Send the link to the women in your life who are self-conscious about this sort of thing.
OK, but let's talk about fixing this one that's already in the can.
You have two issues here to try to fix: One, the shape of the neck/chin/jaw; second the lighting and tone of the neck/chin/jaw.
Using liquify to reshape it is only half the battle. You'll also gently use dodge and burn (mostly burn) to adjust the lighting under the chin and jaw.
I do most of that work in Lightroom, using some custom adjustment brushes, so I can't give specific advice on doing it in Elements. But, you're going to imagine - "What would the shadows look like if that little roll wasn't prominent? Where would the shadows from her chin and jaw fall?"
Darken those bright areas directly underneath her chin and jaw. Don't overdo it or it'll look too fake and obvious.