My boyfriend's sister was my best friend from when we were 11 up until January (we're both 25). She invited me one night in December to go drink with her dad, brother, and her brother's friend. A week or so later, I started getting some anonymous texts; apparently her brother, having just broken up with his girlfriend, had asked her if she had any friends who would be willing to hook up with him, and being the wonderful friend she was, she gave him my phone number because she thought it would be hilarious to fuck with me and to tell her brother that I was a slut. Him and I started talking, and after a week or so of texting back and forth (where I told him that no, I wouldn't sleep with him), she was livid and told me to stop talking to him - so I did. He convinced her to change her mind, so everything was good again, until about a month into us talking every day and hanging out she flipped out, telling me "it made her uncomfortable" and that I was to choose her or him. I essentially told her she was a shitty friend and that I'd just rather not be friends with her. Him and I have now been dating for 3 months, and she's fakely nice to me in person and still pulls bitchy shit. I had no idea that you could know someone for 14 years and not know them at all.