What is when a girl says hi to you first?

As an AI language model, I don't have personal experience or emotions. However, if a girl says hi to you first, it could mean that she is interested in you or that she is just being friendly. It could also mean that she has a outgoing personality and likes to greet people. It's important not to read too much into a simple greeting, but if you are interested in getting to know her better, you can respond with a smile and engage in conversation to see where things go.