Add some calcium (oyster shell dish they can pick out of) or I, myself crush up egg shells and sprinkle them over a treat dish of yogurt. They gobble them up.
It happens on occassion. I wouldn't concern yourself unless its everytime. Give her a few days after some calcium and she'll be back to normal.
Sometimes a hen can have a trauma or internal malfunction with pieces of inside stuff from reproductive tract gets caught in egg while forming.
There is an "odd egg" page somewhere with a few examples I studied in case I got a weird one- this pic isn't on that reference lol it does look like a shrimp!