Final answer:
The word 'nor' is the correct choice to complete the sentence as it introduces an additional negative statement, following the negative form of the first part.
Step-by-step explanation:
The correct word to complete the sentence "She could not speak, ____ could she understand anything we said" is "nor". This conjunction is used to introduce a further negative statement. In this context, 'nor' is the best choice because it continues the negative form of the first part of the sentence and joins it to another negative statement about her understanding, indicating that both speaking and understanding were not possible. Examples of similar usage include sentences like 'I can't speak French, nor can I speak Spanish' to emphasize the inability to speak either of the two languages.