One Hen has bigger bottom than others...

[The Chick Addict]

Chickens like to throw little surprises our way from time to time to see if we're paying attention. Of course we notice when something is slightly off normal, but one single thing will make it into something we should be concerned about, and that one thing is behavior.

If you see a bloody yolk, if behavior is normal, then chalk it up to a broken blood vessel. If you notice a fatty deposit below the vent, if behavior is normal, the hen is just packing some extra fat cells. If you see a puddle of runny poop, if there is no chicken acting lethargic, it's just a puddle of poop.

If, on the other hand, you notice the things I mentioned above and you see you have a hen acting sick, poor appetite, etc, then you have something you need to address.

Fatty deposits are not ideal, but some hens seem to be heavier than others in spite of being fed well with closely monitored treats. This isn't concerning in itself. But if you see a distended abdomen, the area in front of and between the legs, especially if the swelling pushes the legs apart causing the hen to waddle like a duck, then you may be seeing ascites, another name for liver disease. This isn't good. This hen will probably have only months left to live.

If a hen has a substantial pocket of fat below the vent and behind the legs, and especially if the skin appears red and the hen acts sick, that hen may have a chronic reproductive infection that might respond to an antibiotic if it's early enough to treat.

If you actually cracked the egg open and it was a hard shell, then it was very likely not Lash Egg (Salpingitis), but an egg with a tail.

It sounds like your hen is probably doing o.k. - she's laying eggs, is not lethargic, looks like she waddles but yeah not really...

She may have a bit of extra fat and she's getting a little older, so I'd monitor her for now.
See that she's eating/drinking, check periodically to make sure her crop is emptying overnight and do routine checks for lice/mites. If you notice any of these issues, then address them quickly.

The link you posted previously looks more like an incased Intact Follicle https://www.backyardchickens.com/threads/what-is-this-gross-picture.1590786/

Thank you both for your great information! I suspect that it may be the same occurrence from the link that I found. I will definitely keep an eye on her and will come back here if she seems sick. Thank you all again!