Is that a soft, or hard shell?
It is possible the shell has caused an internal injury.
For now, I'd treat her like she's eggbound. Do you have any liquid calcium (preferably with vitamin d)? If so, give her a direct dose to help with muscle contractions to push the rest of it out and get her to a quiet secluded spot where you can monitor her.
Plop her down on some old towels or paper towels so you can heep an eye on what's coming out - more egg, egg shell, or signs she may be bleeding.
I've not had a break 'inside' any of my hens before, so others may have a few additional steps here around getting all of the shell out.
If it has caused an injury, it might become infected over the coming days, so keep an eye out for localised fever around the abdomen (compared to another hen - they do run hotter than us) and lash egg material (pus with consistency ranging from cottage cheese to rubbery egg) - you may want to preempt with antibiotics, or have them handy to help at the first sign of infection.