I was just on my computer, which is right by where all the turtles live, and I was watching my femaleRESswim about, when she stated eating something, and it was an EGG????
It has to be hers, too , I men, she lives alone! I've never never seen her do this before, or with my YBS either?? Did she just eat her own child? 
The last clutch wasn't fertile (as much to my breeding inexperience I judged as close as as possible) but who's saying this egg wasn't?? Is this going to hurt her??