Disclaimer: these are not stiff rules.
If she makes an effort to look at you (by turning around, rotating her orientation) and doesn't SNAP back to her previous position like something scared her, she's interested.
If it's longer than .5 seconds, she's interested.
If she looks at you, then quickly down she is interested.
If she looks at you, then quickly to the side she is neutral.
If she looks at you, then quickly up she thinks she's better than you.
If she smiles, you're an idiot to not go in.
If she makes an effort to look at you (by turning around, rotating her orientation) and doesn't SNAP back to her previous position like something scared her, she's interested.
If it's longer than .5 seconds, she's interested.
If she looks at you, then quickly down she is interested.
If she looks at you, then quickly to the side she is neutral.
If she looks at you, then quickly up she thinks she's better than you.
If she smiles, you're an idiot to not go in.