The Liquefy filter is great for face lifts and boob jobs...!! The jowls are the saggy bits of skin around the jaw line, and under the chin.
First duplicate your background layer and switch it off. On the background copy layer, go to Filters - Liquefy. Choose the tool at the top left side of the window, Forward Warp Tool, zoom into your image, make the tool smaller by using the one of the bracket keys while holding down SHIFT { is smaller and } is larger and gently push the jowls up.
Don't overdo the push or you will distort her face. Zoom back out regularly to see the results before you hit OK. If it doesn't look right first time round, delete the layer and reduplicate the background layer and start over again.
If you really can't do it, let me know and I'll do it for you.