Final answer:
The correct preposition to complete the sentence 'Before you get mad, think about where she is coming ___' is 'from', because it signifies understanding and considering another person's perspective.
Step-by-step explanation:
The correct preposition to fill in the blank is 'from'. The sentence should read: 'Before you get mad, think about where she is coming from.' To 'come from' is a prepositional phrase used to denote someone's background, perspective, or viewpoint. It might reflect their past experiences, thoughts, and feelings. This phrase suggests that one should understand and consider another person's point of view before reacting.
Using each proposed preposition in the sentence doesn't necessarily create examples of incorrect grammar; however, they do change the meaning of the sentence significantly, and 'from' is the most fitting answer in terms of common English usage and the assumed intent of this sentence.
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