I don’t feel an egg anywhere in her pelvis but can feel something hard and possible round way up under her left thigh towards her belly.
I'm glad that she seems to be improving.Reminder, she ate a bunch of scrambled egg yesterday morning too, I think that may be the yellowness?
No, personally I don't think the yellowness of her poop has anything to do with her eating eggs yesterday.
Initially you thought she might be egg bound and felt a something hard and round under her left thigh - do you still feel that?
I am no vet, nor an expert, but some of the symptoms you describe, I would suspect that she is suffering from a reproductive disorder. Which one, sadly, is hard to know unless you lose her and a necropsy is performed - even then some look similar and the names are often confused - so lumping them into reproductive disorder is sometimes the conclusion.
The Corid is a good idea, I would finish with that. If possible, get fecal float to check for worms. While neither of these (I suspect) are her main problem, they can cause complications in hens that are not well. Once you finish the Corid, I would give a direct dose of poultry vitamins (like Poultry Cell) for a couple of days (1cc per 3lbs of weight).
Some hens are able to rally for a while after they receive supportive care - she may have laid internally or has EYP and just needs some time to get back on her feet. Sometimes "recovery" is short lived, while other times they do very well for a good while. Time will tell.
I hope you continue to see improvement, you are doing what you can for her.