What is the appositive phrase in the sentence "my neighbor, little sierra, threw rocks through her parents' window "?

An "appositive" refers to a "noun" or "noun phrase" that renames another noun right beside it.

In the sentence given: 

"My neighbor, little Sierra, threw rocks through her parents' window." ; 
    ,

the phrase: "little Sierra"—renames the noun: "neighbor".

As such, the phrase: "little Sierra" is an 'appositive phrase'.

edmund spenser and john bunyan also influenced hawthorne. : )

i hope this you with your work : )