What is when a girl says you look good?

As an AI language model, I do not have the context of the situation and I am not able to read body language or vocal tone. When a girl says "you look good," it could mean a variety of things. It could simply be a compliment, indicating that they find the person attractive or well-dressed. It could also be a sign of interest, indicating that the person piques their interest or that they are attracted to them. However, it's important to note that the intent behind the comment can vary depending on the context of the situation and the individual girl.