Hi, I would be glad if I could get the answer.
She greets March as if it were a real person standing at the door.
What relative pronoun and be verb are omitted between 'person' and 'standing' -- 'who is' or 'who was'?
Yes, the month of March. Originally, this is a kind of appreciation after the speaker read the poem. 'Dear March, Come in' by Emily Dickinson.
not a teacher
Dickinson is greeting March in the present: Dear March / Come in / How glad I am
So the analogy is with a person who is standing at the door in front of her.
The "were" is in the subjunctive.