A Monumental Mistake

Amy is playing against Nigel in a Modern PPTQ, with her Eldrazi deck. She controls an Eldrazi Monument, an Eldrazi Displacer, and an Eldrazi Skyspawner, and several lands. Amy untaps, draws, then attacks with all of her creatures. While thinking about blockers, Nigel notices that Eldrazi Monument should have triggered and calls for a judge. Amy admits to missing her trigger, but also asks if she can use her Displacer to blink her Skyspawner to make a token to sacrifice. What do you do to fix the situation, and can Amy do what she wants?

Answer
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