Final answer:
The meaning of the allusion 'Benedict Arnold' is a person who is not faithful or loyal.
Step-by-step explanation:
The meaning of the allusion in the sentence 'Rudy said he would help Colleen, but she knew he was a Benedict Arnold' is a person who is not faithful or loyal. This allusion refers to Benedict Arnold, an American officer during the American Revolution who betrayed his country by secretly helping the British. Calling someone a 'Benedict Arnold' implies that they are disloyal or untrustworthy.
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