I understand how you feel, I can be rather smothering with my youngest, more or less mauling him at times....insecurity plays a big part, as I didnt feel loved as a child I think that also is a big factor.
I think also you must feel as though you're not doing a good job, because of the feedback you get from her. Don't worry too much, you're obviously a very caring parent, and don't feel too sorry for your daughter either, she is very lucky to have a loving mum, even if its a bit much at times!! Better that than one who neglects their children.