She didn't put everything, individually, into one egg.

You mash the yolk, and your mayo and seasoning, and fill the egg with the mash. Deviled eggs tend to also be over-filled, not merely topped off.

In this case, that mixture happened to contain bacos, green onion, and onion. The sour cream was placed at the bottom, and the repugnant mash was spooned in.

You could make anything, with any number of ingredients, take a scoop of that mixture, and fill the egg.