Novel. A small child walked out of destroyed city alone

Question

I am recalling the back story of a character in a story. The city where her family lived, (Pretty sure it was Western USA costal city, I get a vibe that it was larger city, Portland, San Francisco, San Diego, etc.)

Her back story was that at the age of 3 or 4 or 5? the city was destroyed and her family died, but somehow she survived. (although probably not unscathed, she may have burns, but otherwise alright)

I dont recall how the city was destroyed, but it maybe something like a meteor or comet hitting it. I don't think it was nuked. I am pretty sure there weren't many survivors.

I believe she just put her back to the fires and started walking, making it about 20-30 miles before she was found/rescued.

I remember nothing of the story itself, she was one of the main protagonists. An adult now and maybe fighting whatever caused the destruction of her home city.

I know there does not seem to be much sci-fi in this description, but I mostly only read Sci-Fi and Fantasy, so am sure it was a Sci-Fi book.

Answer 1

Interestingly, the one that sprang to mind for me was another John Ringo, which is Citadel (Troy Rising #2):

Her earliest clear memory was walking. Walking and fire. She sort of had a vague memory of being somewhere with her mom and dad. She was pretty sure, thinking about it later, that it was a mall. And that was about the only real memory she had of her dad. The first clear memory was the walking. And the fire. And the smell of things that weren’t made to burn. And a sky that was a strange red. Like it should be dark but it was red like a banked fire. And ash. Thin. Light. Constant.

The city in question was Los Angeles, and was destroyed by an attacking (possibly conquering) civilization. The book partly follows her and her journey through the spacy navy as a pilot.

Answer 2

I believe it was Into the Looking Glass by John Ringo - Goodreads.

When a 60-kiloton explosion destroyed the University of Central Florida, and much of the surrounding countryside, the authorities first thought that terrorists had somehow obtained a nuclear weapon. But there was no radiation detected, and, when physicist Dr. William Weaver and Navy SEAL Command Master Chief Robert Miller were sent to investigate, they found that in the center of the destruction, where the University's physics department used to be, was ...

The little girl in question is named Mimi and comes walking out of rubble a few blocks from the explosion to meet investigators. Later will become an important part of the story, though will not be one of the central characters of it.

I do recommend the book, the whole series, actually - named The Looking Glass or Voyage of the Space Bubble - but be warned: this one has more science in it (both applied and theoretical, with much more of the latter, of course), than quite a lot of people is able to cope. But with help of The Internet, it works, and a lot of it is usually dumbed down in dialogues.