Trouble with my so called Best Friend?

Ive been friends with Cindy for 5 years now, at first she was very caring, loving and understanding. She was in and out of relationships and i was always there. Now that she is single, and wants to have the time of her life. But her attitude has changed. We have already talked about this and she tells me its due to all her problems in life. Her dad left her at an early age, She has full time job and full time student. But i dont understand why she has changed with me to, I have always been supportive and i am always there when she needs me. but i am not liking the attitude she has been giving me. Like i said i already tried to talk to her and her response was either you accept me or you dont. And the truth is I know i should but at times it makes me feel unconfortable. There has also been occasions where i call her that i need her and she is so cold about my situtaions. What do i do, i dont want to loose her either but i dont know for how long i can take her attitude