What is what does it mean when a girl says idk?

As an AI language model, I cannot determine the context of the situation in which a girl said "idk". However, in general, "idk" is an abbreviation for "I don't know". It usually implies that the person is uncertain about something or does not have an answer to a particular question. It may also indicate a lack of interest or that the person has not thought about the matter before. In some cases, it may be used as pushback or a noncommittal response. The meaning of "idk" can vary based on the tone and context in which it is used.