I Never Thought It Would Be Like This

I love my husband and kids.  I consider myself a great mother and that is one thing I will brag about  I am proud of myself and I should be.  I'm not trying to sound "prideful", I'm really not.  Something happened that made me think that maybe I'm not as good as a mother as I thought I was.  Two weeks ago my husband and two kids went out of town.  I stayed home as I had to work.  I had 2 days to myself and I missed them but it was wonderful.  I was cleaning my daughter's bedroom and noticed some empty water bottles under her bed so I pulled them out.  Along with them came a notebook that was open and I saw the words "my mom drives me crazy".  Of course I had to read it.  I couldn't stop myself.  I wish I hadn't.  She had written she didn't love me, wished my husband and I would get a divorce and I would leave.  I could not believe it!  Granted she is very close to her father and the definition of daddy's girl.  We are so different.  She is a tomboy, into sports, etc.  I was what you call a "girly girl", more into clothes, etc.   We've never been close since she's gotten a little older.  I cried that entire night then I got angry.  How dare she?  I have done so much for her, sacrificed so much to make her happy and she feels like this?  I thought and thought of what I could do differently and know what I found out?  Nothing.  There is not one thing I would change about myself to make her happier.  I don't need to!  She is a good girl, never back talks, has never been disrespectful to us.  I have never raised my voice to her.  I just can't figure it out.  Maybe she was mad at me that day or something but she actually wrote "I hate her".  Hate is a very strong word and I never once even thought I hated my mother.  Sure I got mad at her and maybe at times didn't like her very much but I never hated her.  This is really bothering me.  She is acting better towards me now and I don't know why.  I'm not doing anything different.  I asked my 17-year-old son if he thought I was a good mother and he said I was the best.  He has always said he's like to have two good parents as some of his friends don't.  Anyone out there have any advice?  Anything like this happen to you?