yes a good OMEGA 3 fatty acid is excellent for skin and coat issues, I will include the name of the best brand for use with cats...contains no artificial sweetners, no preservatives nor colors, no gluten, wheat or yeast.....squirt one gel cap into the food
http://www.iherb.com/Natural-Factors-RxOmega-3-Factors-EPA-400-mg-DHA-200-mg-120-Softgels/2717
excessive licking can also be caused by allergies...usually to something in the environment. what kind of litter do you use? be sure its a scent free type.
what do you use to clean your floors with? most cleaners are full of chemicals, try just vinegar.
do you use household scents such as candles, room freshners, scented dryer sheets, perfumes, cigarrette smoke in the house?....anything with a scent to it...a human as well as a cat can become very sensitive to many things...try eliminating everything that you can.
http://www.cat-health-guide.org/cat-allergy-symptoms.html
Give her a vitamin with a lot of minerals.