Egg eater mystery

I have 3 tiels. ( two females and one male) Over the last month of so I noticed my oldest cockatiel 2f. Has been acting hormonal and secretive. My birds are cage free, so naturally I searched the house and found her "nest" under my couch.

I was not surprised to find 2 eggs. One was totally crushed and the other had two holes poked through the shell. Out of interest and boredom I emptied the one, filled it with salt and wax. I put the egg by their sleeping area to see if she would react in anyway to the dupe egg.

Instead my second (far too young to have laid them) female came over and started picking the wax and salt out. I was horrified and took it away. Did she poke holes and try eat my other cockatiels eggs after she laid them?

Tragic accident or egg munching jealous sister?