I had this happen with my head hen/best layer. From the time she started laying in Dec of 2016 she missed a total of 2 days upintil Novembet 2017! Her shell began to get a bit thin and sort of crumbly around August 2017 to yhe best of my recollection. Little crush marks would appear with the SLIGHTEST pressure. She's a young hen so it wasn't age. She also had ACV in her water consistently, good layer food, good calcium (egg shell and oyster... Hen's choice) and ate plenty of both.
Before her molt last fall, she started to become egg-bound. She laid a couple of rubber eggs that took intervention to purge. I took her to the vet and paid $300 to have her implanted so she would't lay for at least 4 months... Well, it lasted 2 and a half months, lol! She molted, took a couple months off and started laying again in Late Jan/ early Feb of this year. So far, her eggs are good! Strong (if SLIGHTLY thin) shells with just a tiny bit of calcium deposit on top. Now my other EE, who DIDN'T molt last Fall and who has been laying consistently for about a year is starting to get thin shells like my head hen had. I think times their bodies just need a break!
How long did your girl stop laying during her molt?