It's not a good sign that she's taken a turn for the worse. The yellow discharge is also a bad sign that either an egg has ruptured or there's infection in the oviduct.
To give you a comparison, I have a hen right at this moment in a crate in the garage after observing her acting "off"...
What may feel like fluid, could be fat. If you were not going any deeper than half and inch, if there was fluid you would have been able to withdraw some. Sticking the needle in deeper than that, you may have hit an organ. That would have prevented hitting any fluid. Abdominal fluid is just...
You just found out that she has no fluid buildup in her abdominal cavity. That rules out ascites and probably EYP, as well. But she may have some other bacterial infection. Do you have any of the antibiotic left? What dose were you giving her?
I would suggest aspirating a little fluid and see what color it is. That will tell you more than just guessing where the swelling is and what it means.
Take a needle syringe and wipe the puncture site well with alcohol. insert the needle no more than half an inch and pull back the plunger until...
Is the swelling in front of her legs? That would point to ascites. If the swelling is behind the legs and below the vent, it would point to EYP.
You can aspirate a little fluid and take a look at the clarity and color. Mostly clear fluid is typical of ascites while brownish smelly fluid is...