Answer:
Use a comma to set off a phrase or clause at the beginning of a sentence.
Step-by-step explanation:
The sentence is made up of two clauses: a dependent clause which is "Although she loved her parents" and an independent clause which is "Sarah was eager to leave for college and be independent."
The grammar rule is that when a dependent clause or a phrase comes before an independent clause, a comma must be used after the dependent one or phrase in order to separate both groups of words. Here's the correct version of the sentence:
Although she loved her parents, Sarah was eager to leave for college and be independent.