Hey
@Egger Allan Poe
I like your user name!
Great that you've sought advice here. 'He' is not a rooster, she is just an old hen who has stopped laying, bless her.
I think you need to prepare yourself for the end of her life. She has had a good 8 years and I can tell she has been taken good care of because you care so much about her welfare.
For a breed that lays a LOT of eggs, she has done really well to make it this far. I suspect the lump is a goiter or the saggy crop as mentioned before, but she is thin, thin, thin. And her body is giving up on her, she doesn't want to eat or drink or do chickeny things and be out with the flock.
You may be able to prolong her life by hand feeding her water and food, crop massage, etc, but it won't be for long and she hasn't got much 'quality of life' has she.
As hard as it sounds, you should give some thought to euthanising her. It may well be the choice between a quick end (with love and kindness) and a long drawn out one where she gets sicker and weaker. That is a lot for a 14 year old to deal with. Are your parents involved with the chickens? Can you talk to them about different options?
It is so sad when they get really old and sick like this (I cry over them every time), but I'm sure you understand that it is inevitable.
If you were my child, I would be so proud of you, having sought advice, researching, nursing and caring for her like you have.
I hope you don't think I'm being patronising. You've done great, but you may need to make the hardest decision now for her best interests.
Sending positive vibes.