I’m sorry to hear about your hen :hugs
Thank you for updating the thread also.
When people think of a chicken being eggbound they often think of the egg getting stuck close to the vent which is an emergency because it also blocks their ability to poop and impacts nerves and circulation etc...
If it’s an option you can try the suprelorin implant which is a hormonal contraception that stops them from laying for about 3 months. For some hens it only lasts one month and for others up to six, so it is variable.
It won’t cure any underlying issue such as infection, cancer, any egg mass or...
They do tend to pull their head back when they feel poorly which may emphasise their throat. Does she lay eggs? 4yo is pretty good for an ISA; as a production breed they are susceptible to reproductive issues.