Is it wrong to call a married girl 'baby'?

One of my friends, a girl, who is marreid used to respond to me positively whenever I called her "baby". But recently she told me I should not call her so. Why did she not tell me this at the first instance itself when I called her baby? I do not give it much meaning and just show it as a symbol of my friendly and brotherly affection to her. I am married and one of my email girl friends, who is not married, calls me honey and dear, and I do not feel excited or some thing extra ordinary. What is wrong with some women?