She became aware of something. She became aware of a pending event. If she had been a member of the chosen species (whatever that is) that event would have been a good one, a blessed one, a wonderful thing.
What is missing from the sentence is what she did when she became aware of the event. When she became aware of the event, she...
Hi, When she became aware of the coming of what would have been, had she belonged to the chosen species, a blessed event, and told him about it, he snarled.