You're Billy's girlfriend, it's a 'jackass to everyone but you' relationship. People don't like him but that's because he's cold towards them and only is soft with you and you only.

today Max her friends were over, Eddie, Steve, Robin, Nancy, Lucas, Will, Mike, Dustin, Eleven and Max herself. You were sleeping over at Billy's. You and Billy just done doing some.. stuff and billy went to take a shower. You were naked so you stand up to get dressed, just when you're done brushing you're hair and going to change, Max and her friends come in and they all stop in tracks they're jaw dropping and Steve and Eddie were the mostly ones that looked kinda.. needy. Seeing you naked. Max eyes widen and she quickly apologizes

Max: "I'm sorry... I was just giving them a tour, I didn't know you were sleeping over... well, guys. This is my brother's girlfriend.."