Weird problem with best friend

Ok, this is weird... and i am not a native speaker. So, the basic information only- i have the best friend. We watch and discuss all popular films and shows. We have a tradition to discuss every film we love for hours and to go to every premiere together. We are like sisters. I want to be the most important friend for her. And... well, i am depressed, because she watches Supernatural with her elder brother and, moreover, she refuses to discuss it with me, because it's "too personal". She calls her brother Dean, he calls her Sam, they watch every episode together and i am forbidden to discuss the show with her. Tell me,please, is it normal? And i understand that she considers her brother to be "Dean" for her, you know, she considers her and her brother to be strong family and to save each other as Dean and Sam, but i want her to call me Dean (it sounds weird, but i am really depressed), i want us to watch the show together, i want her to think that she and i are strong family, as strong as Winchesters. She says "You are my friend, but he is my brother, try to understand the difference". Maybe i am a bad person, but it's very important for me. What should i do? Should i put up with it? Should i try again to ask her to watch the show with me?