Am I a Failure As a Parent?

I never wanted the relationship with my daughter that i had with my own mother, so i tried very hard to be closer with her, to ensure she considered me not only her mother but also her friend. (she is now 24yrs old) and yesterday she told me she never wanted that. she wanted me to be more of a mother not her friend and a friend to her friends.  she said she always felt threatened by this. and she thinks this is why when ever we are around each other or even talk on the phone she is short with me, and gets angry, she also feels that her fathers and my divorce didn't help. she wants to fix this prob. but neither one of us knows how. I feel when ever i speak it is wrong, that i embaress her, she says what ever i say it is something obvious.  She also gets mad when i joke around and say that she is my experimental child. as she is the oldest of 4, and i have learned what to do and not to do through my mistakes in raising her. she is a beautiful woman who puts cindy crawford to shame, and honor student in her 3rd year at college, holds down 2 jobs and is getting married to a wonderful man, but i don't know what to do anymore, she says she doesn't know why she is angry with me, because i am always polite, kind and considerate to everyone, but ....?  I told her i think she wants me to be something i am not, or to be more like some one else's mom. she denied that. we try to talk but we start crying, and i am afraid to say anything and she'll just get mad and hang up.  what is the next step...?