Can anyone help diagnose this issue?

[Dad of chicken lover]

Worms can affect the overall health of the bird. But it sounds like she's happy and well within herself. This is why I suggested getting a fecal float to see if worms were even an issue.

When she stopped laying, did she molt? Grow new feathers?

Check her over for lice/mites, see that her crop is emptying, just so you've covered some of the basics.

It can be hard to know why a hen isn't laying eggs. Each one is an individual, even within the same breed. Some take a break for a long while and resume laying like gangbusters. Others may lay for a period of time and never lay again, but live for years.

No, she didn't molt or new feathers when she stopped laying. Just the two larger elongated eggs within a week or so of each other (only two ever by her) and then the one VERY strange egg followed by nada. The strange egg was quite fragile but came out whole which makes me think there isn't an obstruction. My daughter holds her/then a lot and I believe would have noticed mites but will look.