I know how you feel OP, but I think my situation is worse than yours though. I love my dd (12), but sometimes I don't like her very much(I cannot even begin to describe how much guilt I suffer because of this). Like your dd, she is also constantly complaining about all kinds of aches and pains, no matter how trivial it is. She cries at the same volume for everything, whether it is a paper cut or major tumble. I think it has a lot to do with the arrival of my ds when she was 4 years old. I often explain to her that for the first four years of her life, she had me all to herself, but that her brother never had that opportunity, as my attention was then shared between the two of them. I have to remind her of this, because she always acts like she is somehow being done in, that she is being neglected, the injured party, if I don't drop everything to attend to her every demand (it drives me nuts).
I too find it very hard, at times, to hide my irritation with her. She makes me feel overwhelmed and helpless and inadequate most of the time. It is almost like she is constantly comparing me to her friends' mothers and that I come up short.
She is the most wonderful child, bright, beautiful, talented, funny and loving and I don't understand why I feel so annoyed by her at times. She also has no concept of personal space and I find myself pulling away from her when she wants to be close to me. I give her lots of hugs and loving affection, but it is never enough for her. She hangs on me while I am trying to cook etc. I don't know why this irritates me so.
Also, she is a very unaffected child. She is never happy to see me arrive or sad to see me leave. She happily goes for extended sleepovers at her best friend's house, without phoning me once.
Sorry, didn't mean to hijack your thread...what you've said just struck a chord with me.