There are grammatical restrictions on the use of pronouns when they occur within the same sentence as co-referential noun phrases. A pronoun can co-refer with another normal noun phrase if either:
- it occurs after the other noun phrase
- it occurs lower down in the syntactic tree than the other noun phrase.
This last point means that a pronoun in a subordinate clause can co-refer with a noun phrase in a main clause regardless of whether the subordinate clause occurs before or after the main clause.
However, the rules above do not allow a pronoun to co-refer with another noun phrase when the pronoun comes first and the pronoun is in the main clause but the normal noun phrase is in a subordinate clause:
- She made dinner when Brenda got home.
In the sentence above she cannot refer to the same person as Brenda. We can compare that sentence with the following:
- When she got home Brenda made dinner.
- When Brenda got home she made dinner.
- Brenda made dinner when she got home.
In the examples above she and Brenda can refer to the same person. In the first example, this is because she occurs in the subordinate clause and Brenda occurs in the main clause. In the second example, it is because she occurs after Brenda. In the third example it is for both of those reasons.
The Original Poster's example
Sally had been the first one to greet Paulina when she appeared in the doorway.
The sentence above is clearly ambiguous because she can refer back to either noun phrase in the earlier main clause. We can use the rules of grammar so that we still have one she, one Sally and one Paulina, but without any ambiguity. To do this we need to move the subordinate clause to the front of the sentence and put the proper name in the subordinate clause and the pronoun in the higher main clause:
When Sally had appeared in the doorway, she had been the first one to greet Paulina.
When Paulina had appeared in the doorway, Sally had been the first one to greet her.
Notice that in example (2) we are also guided by the rules about reflexive pronouns. Apart from the common sense idea that Sally wouldn't be greeting herself, Sally and her cannot be co-referential because they occur in the same clause. If Sally was co-referential with the pronoun, the pronoun would have needed to be reflexive:
- When Paulina had appeared in the doorway, Sally had been the first one to greet herself.
Pronouns are quite interesting, aren't they!