Amber Stars are bred to be in continuous lay for a relatively short life span, Feetrus. If she were living in a commercial setup she would have been 'harvested', along with all her friends, at 18 months to 2 years old, when the farmer would expect egg quality and numbers to be declining, at least in enough of the birds to make the enterprise uneconomic. It's at this point that a lucky few find new homes as exbatts, some going on to lay for a while in more relaxed circumstances, though most get made into dog food etc. So actually your girl is lucky to have made it this point and beyond, even though she may be one of those who reach the 'henopause' relatively early in her life. I don't think worms are likely to be a big issue if she has been having her Flubenvet regularly, and although calcium balance may be involved, as Chris says, this is complicated in hens as calcium uptake declines in what to a hen is old age. I wonder why she got bad worms last year? Could it be that she picked up a lot of earthworms from her free ranging and ingested too many chicken worm eggs from the earthworm intermediate hosts?
My feeling is that this is more a consequence if her genetics than anything else. Egg problems are common in these kinds of hybrids, they just live life in the fast lane and delight you with daily eggs for quite a while, and then abnormalities set in, such as prolapse or thin shelled eggs or strange things like what yours is doing. I would keep a careful watch on her, in case she looks poorly. Is hunched up or immobile, and moves on to being eggbound, prolapse, or peritonitis, but as long as she seems OK, there's not much else you can do, I'm afraid.