Complete noob here. I'm very short - 5'3. My legs are really short (didn't measure).
I just bought a Schwinn Coronado online but it's too big. I was reading the manual and saw the sizing chart and the test where you stand up over the bike and you should have at least 2 inches of space. It went right up into me nads while I'm on my tippy toes
I would think that a 15" frame would be best for you. If you are getting another bike (I presumed you sent the other one back), I would look at this one... http://www.bikesdirect.com/products/.../jub_dlx_x.htm It has an adjustable suspension seat post and adjustable handlebars. You should be able to find a good riding position on this bike, They also have free U.S. shipping and no tax, unless you live in Texas.
Bikes Direct has some great deals on bikes. This bike is, in my opinion, heads and tails better than the Schwinn you were looking at. They have a 16" that they say is good for most riders 5'4" to 5'9".