Answer:
She traced her ancestry back to the original president of the college, which her roommate thought was unfair.
Explanation:
In this sentence we have the personal pronoun she and the weak possessive pronoun (or known as possessive adjectives as well) her.
We are remarking here that She (woman) and therefore we will use Her (belonging to a woman). This is a simple way of making the pronoun reference clear; remarking with another color, underlining, circling, etc...
