Oh noooo Pappy..... this sounds like dropsy 

Do you have medicated food to feed with?

Hope Minde will be on soon, she knows much more about it and how to treat, also Nossie.

I'll keep fingers crossed that all will be fine

I think you know how to treat, you're pretty resourceful.  But anyway this is what we did when my sisters fish, recently had dropsy.
1) Raise the tank water to 80F
2) Add Epsoms salts 1/4 tsp per gallon of water
3) Added Marcyn II ..this worked the best. Gave two consecutive treatments according to pkg directions.
4) Feed Antibiotic medicatd food ONLY for 2 weeks.  We used Jungle brand.

Fish made a full recovery and is still swimming happily!

Her/his belly is very round like a ball and it doesn't look normal like the rest of the fish.

You separated her to a hospital tank, right? It's important that you treat only the fish that needs it when such strong medicines are needed.

Wishing you the best Pappy with your poor sick little fish, hoping the treatment will be a success.

My favorite fish had dropsy and have a few hopefully helpful words for you:

If what you're dealing with really is this disease, you have to maintain perfect water quality. Dropsy can be caused from a liver failure and if that is the case the chances are slim your fish will survive. Other causes could be bad water quality for a long time, a bacterial infection, parasites, or even cancer. Overheating can also trigger dropsy-like symptoms. It is imperative to treat this early on. In later stages the fish will be unable to eat or keep food down. Try to avoid stressing the fish as much as possible.

When my fish had dropsy I found lowering the temperature helped. It slows down the heart rate of the fish and the scales tend to flatten more against the sides of its body.

If you decide not to use medications, a natural remedy that helps the fish not be so stressed is garlic. It also helps with bacterial infections, lowers blood pressure, and generally sooths the suffering animal.

Are you seeing any blood hemmorhaging/red ulcers on the body, fins, or head? If so, you know it's getting worse. Remember that problems like this are often very hard to treat. If you know the fish is not going to make it, I would advise you to consider putting him/her down to relieve it from its pain. But hopefully he'll make it!!!

Good luck and fight the good fight

Keep fingers crossed that she's getting better

Oh good, I hope she will recover quickly.
I like that Fungus Eliminator by Jungle I must say.
It sure works good and will cover any secondary infections too.

That is wonderful!
I think you caught it soon enough.
She should make a full recovery!!

Glad you caught this early and have been able to treat it so well Best of luck!

Goldiegirl: Total karma for you! That's a very helpful post It's always good that someone with experience in treating a disease come forward and helps

pappy: I'm so happy for you!! That's great news!! Just be sure you treat her until all symptoms will go away

Nossie: Thanks for the karma! It's funny how looking back on my fishkeeping experience I can see how many problems I've encountered. I lost Elsie Amber due to Dropsy - surprisingly not through any thing I did wrong...I bought  her that way and didn't notice the slight 'pineconing' of scales. The owner of the shop wanted fifteen dollars for her, but for some reason lowered it to eight when we asked if we could buy her...suspicious right? Well soon enough she was very ill and it had gotten to the point where I couldn't do anything for her and we had to put her down. In the process I found out a lot about the disease though, so it was a good experience.

pappy-fish: great to hear your china doll is making a comeback!!! yippee and good job!!!

Goldiegirl: That's just plain... mean! I think the people in the shop should've warned you that she was sick!
They did that here when we wanted some clown loaches, they refused to sell them since there was an outbreak of ich going on in their tank.

Absolutely! I really avoid pet shops that are unpleasant to visit, as in, you notice that the people don't know what they're doing, or the tanks look unfresh or... you know.
Nicely enough, I've got some pretty good contacts in the pet shops I visit And I find that a huge plus! I can ask for anything I need in all of them

My China Doll is happy and healthy again. 
Thank you ladies for your advice and support.