Yep... we all have a date. She was surrounded by her kids and happy. Perfect ending! I am sorry she left you so sudden. Looks like her legend will carry on in her peeps!
Sudden can come from some type of poison, plant or otherwise.
She is pretty old but I would think if age played a factor she would not be hatching out babies.
And what type of chicken is she?
BTW... I recently lost a chicken like this. All happy at bfast and by lunch dead. Necropsy showed she...