So basically, me and my boyfriend have been together since july, and in september a girl transferred into our school. Me and her are really close friends. Around october, i started to notice changes. I started to notice she had been talking about my boyfriend more etc acting different around him. Then in january the alarm bells started to go off. After a party, the two of them walked home together. And she got in serious trouble with her parents because she was meant to get dropped home by a friend, but instead walked with my boyfriend. Also asked him who he'd get with if we weren't together. Ever since, shes been posting aggressive tweets whenever he doesnt text her back and does things to get his attention, e.g. Blocking him on social media for his attention to see if hed notice etc. I'm not imagining it either, bc shes told a few people she likes him. It really gets to me, and i feel like an awful friend when i get angry bc i guess i should be more understanding? Help please?