So good that she's eating and pooping fine - that's a great sign. If she was egg bound, she would probably have some problems with poop, as the stuck egg would tend to (to a lesser or greater degree, depending on how close it was to the vent) block the passage of faeces. (Our poor Bella made one hell of a mess on our vet's table when she finally emptied herself of the stuck soft shelled eggs that were bunging her up!) It does sound like, even if there is a soft shelled egg in there, it isn't near the vent, or you would probably have felt it with your finger.
And yes, internal laying is also a possibility, and can cause the hen to suffer the same symptoms as a case of egg binding would. The odd egg you described from yesterday could be suggestive of some weird laying stuff going on inside her, sure. (Internal laying can be a chronic condition which some hens live with for a while - it doesn't always have to be an acute emergency, as really, once the egg is inside the abdomen, there's not a lot the vet can do to reverse that state of affairs. In this case though, she does look quite poorly, in an acute sense, so the vet is IMO a definite option.)
It's very difficult to say in this case - the fact that she's hanging out with the other birds, and eating and pooping fine is throwing me a little - they do tend to go downhill quite fast and stop eating and being active if they are egg bound, I can vouch for that. You probably do need to persuade that vet to see her, if you possibly can, to get a proper diagnosis.
Very best of luck - she's a beautiful girl and I do hope she's well again soon. Keep us informed of her progress...