1) A song by KISS
2) An unbelievably awesome girl, always happy and laughing. Despite this she can also be serious when you need her to be and will always be there.
3) A compliment
"have you heard that song, 'Beth'?"
"DUDE, Have you seen my beth?" "Yeah, she's over there being awesome, laughing and making the world a better place."
"Wow, you are such a Beth!"