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

As an AI language model, I cannot determine the intentions of a girl when she says "hey". However, in general, "hey" is a casual greeting used to acknowledge someone's presence or to initiate a conversation. The tone and context of the conversation can determine the true meaning behind the greeting. It could be a way to say hello, catch up after a while, or to show interest in the person they are addressing. Ultimately, it is essential to consider additional nonverbal cues and usage throughout the conversation to understand the full meaning behind "hey."