Throughout the poem, the speaker uses fire as a motif. What does this motif most likely represent in the poem?

There are many different interpretations of what the poem means, and particularly what the fire motif represents. One possible interpretation is to look at the narrator as revisiting the scene of a childhood trauma. (Whether or not it was an actual fire.) She is all alone; there is a palpable sense of loss. Her parents are notable by their absence; yet their personal belongings—their clothes, their used dishes—still remain. These personal items add to the narrator's grief. It is difficult enough for her to return to the scene of what appears to be such a terrible tragedy; but it is even worse to be reminded of her parents. Their memory haunts the place; their ghostly presence disturbs her mind. 
But fire doesn't simply destroy. It also purifies. And having gone through the trauma that robbed her of her parents, the narrator is now finally able to construct a life of her own from the ashes of a painful past, one that delves deep into happy childhood memories from the time before her appalling loss.
https://poets.org/poem/morning-burned-house