Salpingitis is inflammation of the oviduct. Ascending infection means they think the bacteria was introduced through the cloaca and traveled up the reproductive tract. Then the infection spread to the blood and from there to the liver where it causedcell death. Coelomitis is the medical term for egg yolk peritonitis. E. coli is a common bacteria of the GI tract that doesn't usually cause any problems as long as it stays in the GI tract. From what I can tell, Gallibacterium anatis is also a common bacteria present in healthy chickens that is opportunistically pathogenic (disease causing).
Can you contact the veterinarian who did the necropsy for clarification and recommendations? I've been out of the field for several years now, so it would be better to get interpretation help from the vet who did the necropsy, but from what I'm reading her it seems likely this shouldn't be an issue for the rest of your flock. It sounds like she's had a reproductive issue that allowed normal bacteria to get out of control and that led to systemic infection (sepsis) which her body just couldn't handle.
