[kideafish]

Just to say check her anus for any red 3 pronged string like worms hanging.
She may well be full of worms !!
Check her faeces if possible and try and quarantine her to enable you to do this.

She may also, as Cichlid man said, be constipated.
Do try and reduce the flake feeds and supplement with frozen brineshrinp once a day only. Brineshrimp does help with constipation.

Hopefully she wont have an internal infection and nematode worms can betreated but let us know.
If it was Dropsy then she would have scales sticking out either side like a pine cone effect so it cant be dropsy.
I doubt she is egg bound and fish can carry this huge stomach full of worms for sometime.

Good Luck