Answer: subjective is the answer
This is punctuated correctly.
"Marshmallows are my favorite snack" is a complete sentence unto itself.
The comma instead of a period shows that the sentence spoken is part of the whole sentence, which includes the speaker (she) and a word to describe how the speaker said it (explained).
The author's word choice gives the reader insight into the dialect of the speaker. The written pronunciation of some words show what the character would sound like speaking, which gives an indication of where they are from or what they're like.
