Skinny people have muffin tops too, simply because they wear jeans that are too tight and slip down from the waist to hug the lower waist making them bulge out over the top. So wear jeans and skirts that really fit you well. And then tackle the tummy by making a bet with yourself to cut out anything sweet or fatty until a certain date some weeks or months ahead - I lost loads of weight that way. I kept the booze though - had to get my priorities straight.
Do you have a muffin top when naked? If not maybe your clothes just don't fit properly.
If you do want to slim around your middle something low in processed carbs like the south beach diet ought to do it. If you want to do similar to WW you can try MFP its free and there is a support thread on here.
Have you tried calanetics? It's great for muffin top. It's as boring as sin but does work and works fast! You can get the DVD on Amazon but go for the standard one not the advanced because it's really hard!
Other than that you could be intolerate to something? Maybe cut out glucose for a month, then dairy etc etc to work out what it is.
I recently cut out dairy and caffeine and my muffin top has dissappeared.
Toning reaches the core area but if you are carrying a lot of fat around your middle then results will not be very visible. Need to do a combo of cardio exercise, core exercises AND follow healthy eating - ie avoid foods low in processed carbs. I am now very toned and slim BUT if I eat lots of processed carbs I get bloated and my flat stomach disappears.