The second law of weightloss says: "The less you have to lose, The Slower it will come off"
(boy, I HATE laws like that - don't you?) Regardless which diet plan you choose - with only 15 pounds to shed, you'll need to face this law and succeed in spite of it (because it IS possible!).
I think it took me 2 years to shed my last pound.
Ok, ok, it REALLY only took a month. SEEMED like years, though!
Don't focus so much on your scale. Measure yourself and go by that. Afterall, if you were given the choice of 15 pounds off OR 3 dress sizes, which would you choose?