Hi all potted out
In your sentence ignited basically means “started”. When you ignite a fire, you start a fire. Let’s take a look at some other words in the sentence:
Breath basically means “voice”.
First her voice was heard as a yelp (a very short sound/cry). You might compare the length of a yelp to a spark.
Then her voice became a wail (a prolonged sound/cry). You might compare the duration of wailing to the duration of fire/burning - i.e., much longer than a spark.
So, ignited refers to the start of the more prolonged sound (wailing).