I can relate. My sister was my best friend up until the last 3 years (Im 23 now, she's 30) and she turned into this ..totally religious and condiscending person. Started acting really snobby and it eventually turned into outright hostility that was triggered by almost minimal daily communication until I eventually just had to stop speaking to her altogether to save whatever sanity I had left. She's always needed my parents approval and attention and she tends to manipulate my parent's attention even when we used to argue by drowning me out and having them focus on her issues when they'd tried to intervene until I just walked away.. and sometimes you really do have to walk away there's no sense in keeping yourself hurt over lost opportunities..esp with family members they can just be the most toxic relationships to have