Why do I care !

I am a boy and i am naming the girl as 'x'.I met her in my college.She is not at all a happening girl and i am quite opposite to her. But we proved the fact that opposite attracts !!. We became really good friends and tes we were attracted to each other.When we became friends she was overcoming from a breakup which she did. Her ex was madly in love with her...even till now.As her best friend i tried my best in helping her taking a final decision based on all pros and cons.She gave me the answer that she does not want to go back and to move ahead in life.All things were going good.We also went for a collage trip where we spent most of the time together and we both started falling for each other.I was more interested in her than she was with me but she admitted that 'YES SHE TOO LIKES ME'. I became happy bcoz evrything was going just fine and our friends were also supporting us. Then came a major break. She started interacting with her ex bcoz he was not able to get out of it and she was blaming herself for the situation.I supported her a lot in this and put her interest ahead of mine. Then suddenly one night she said 'I like you just as a friend' and it struck hard.I thought may be she needs some time to get over it and then we will be alright.She gave me valid excuses like if she did not had a boyfriend before then I was the perfect man for her. She was confused between him and me but everytime gave me the news that she always wanted that gher ex should move on !! And she is not interested in him but just as a friend.She told me that she does not want me to be her boyfriend just because if anything wrong happens then she would lose me as her best friend also.I tried to make things right and managed to just being friends with her with the same chemistry.It worked for a while but then we started fighting a lot.Ironicolly fights have always been the best part of our realtionship. Our bond was getting weaker day by day and I was trying my level best to make our frienship work.The thing which strucked me gard was that she was not outting any effort to make things right !!. It became worse and still i saw no effort from her side which demotivated me and I also took a decision and left things the way they were. Next what I experienced was that...that she and her ex are getting back together which devastated me.I consider myself a strong person amd i decided not to say her a word but to ignore her.But when things got right for her she noticed that I am no longer trying to get to her and she started missing me.We have a common group of friends and thats why I cant fully ignore her otherwise it would be the first thing I would love to do. Her thought in my mind makes me sad.Now she does not want to leave me as a friend but i am finding it difficult to make our friendship work. I just talk to her on important things for sharing notes and all or just hie hello talks. I dont know what she feels of me but I know that i care for her as i used to care for her before. I need a suggestion whether to totally ignore her or just maintain a not so good friend behaviour. Ps. She is a nice girl but her decisions fucked us.