You might want to try Christopher & Banks. Their sizes go up to 14, but they seem to run a little large. If that doesn't work maybe CJ Banks. Also try Chicos.
Trudylynne
I find age appropriate clothing at consignment shops. You can get brands like Chicos there, Liz Claiborne etc.
I also like Kohls.
Ann Taylor Loft and Kohl's are my consistent favorites, CJ Banks and Chicos have good things, sometimes, although sometimes they are a little stodgy for my taste, ditto Cold Water Creek. J. Jill has some nice things. I've had intermittent success at Dress Barn. Sometimes I find a ton of stuff there that I like and sometimes not a thing!
To my mind, the most limiting words in the fashion dept. are "age appropriate." What's appropriate is whatever looks good on your body, in the correct size and in a flattering color. Why the heck should the 20-somethings have all the fun??
I agree with Kohl's and Ann Taylor Loft. Their clothes are stylish and comfortable for a size 14. Chicos has great clothes, but I agree with tootandpuggle that they can be a bit stodgy, or in my opinion "borderline matronly." I am a size 10, and I prefer White House/Black Market along with Cache', however their retail prices are very high - good quality though. I find lots of great name brands on Ebay at very low prices, ususally used, but "gently." Even with my size 10 bod, I usually have to buy a size "L" at WHBM and Cache, so not sure how well a size 14 would do for you. Try looking for jeans under the brand name of "Not Your Daughter's Jeans." (NYDJ) These jeans are so flattering for any size and hide the flaws very comfortably. I buy mine on e-bay to save money, because they retail for about $100.