Final answer:
The missing word in the sentence is 'her,' which is a possessive pronoun that aligns with the female subject of the sentence being referred to.
Step-by-step explanation:
The sentence should be completed with the word 'her' as it refers to the possessive form that matches the third person singular female subject 'Nobody appreciates her talents until she is needed to perform the night of the show'. Here, 'her' indicates that the talents belong to the female individual who is the subject of appreciation.