Search Results: attracted to my brother's friend

I am an Indian and in India, we usually call our elders brother or sister to show respect. So a few months back I met this amazing girl at my college. She is my senior. We hit it of from the start. She was friendly and I was not attracted to her at all so I called her sister. We became close. She told me everything, her deepest secrets. I told her mine. As time passed, I realised she was a pot smoker, a casual drinker and a bipolar person. A few weeks ago, something fucked up happened in her family and she was quite frustrated. I tried consoling her but she just backfired at me. A friend of mine came to calm her down. A day later I realised that her behaviour has changed and she has grown closer to him than me. When she started drifting apart from me, I realised that I have feelings for her. I love her and it kills me that she has changed. We don’t talk and I have come to a realisation that I was the only one initiating the conversation every time. I don’t know what to do. I have called her sister and now it’s really hard to think of her in that manner. How to change it? I want to go out of this Bro zone and make her my girlfriend. At the same time, her behaviour is making me want to leave her. I am quite lost. What should I do?