The fish is simply gravid - that overhead picture clearly shows the 'bulge' is to one side (the fish's right side' and to the rear of the abdomen, which is always the case with a goldfish that is ready for spawning - the eggs begin to swell as they hydrate prior to them being released to the lower ovary just before spawning.
Now, if the eggs are released to the lower ovary, but no spawning takes place, then the eggs will rot inside the fish and cause septicaemia and ultimately death - but don't panic as this is not always the case. You have a couple of options here
Was the fish in a tank with others? If so, are there any males? Males in spawning condition should display white tubercles on the head and gills, sometimes also on the pectoral fins and even the body... even if not in full condition, they will often feel 'rough' to the touch.... they also lose much of the body slime prior to spawning. If you have males, you can put her back and spawning may occur. Goldfish may spawn once every few days until all eggs are released.
Option 2 is to wait until the eggs are dropped into the lower ovary - indicated by a very soft abdomen - hold the fish gently upside down and mover her from side to side... if the 'buldge' flops from side to side, then it is likely that spawning is imminent. At this point, a gentle squeeze, pushing the fore finger and thumb either side of the fish, back towards the vent area, will expel some eggs. If eggs flow freely, then it is best to 'strip' the fish like this to remove as many as you can.
Often, if spawning is imminent, eggs will actually fall from the fish when it is lifted from the water.
If you can hold the fish upside down and take a good photo, I may be able to advise you more on whether she is ready for this treatment.
My best advice though, would be to place he back in the original tank where she has more room (to reduce stress) and watch the other fish to see if any start to 'chase' her... these will be the males.
There are several triggers to the spawning process and if these are not all in place, then ... and this is the good news.... the eggs will just be re-absorbed by the fish so as not to waste the immense effort she has put into developing her eggs. She will be carrying several 'year classes' of eggs ready for development when conditions are right, so once her present gravid state passes, the process of developing the next batch (known as vitellogenesis) will begin.
Constipation is normally indicated by colourless trailing faeces - often mistaken for intestinal worms
Hope that helps