Difference between 'omae' and 'kimi'
 

From what i've seen they are both informal pronouns used between friends, but which one is used more commonly? I have also heard that some girls do not like being called 'kimi' while others like it? Just a bit confused...clarifications appreciated! :)

おまえ is used between very close guy friends. Or possibly to a stranger when you want to start a fight. You can also use it to an inferior. It is not used in a formal situation.

きみ is more formal and not used between friends very much, more to an inferior at work. The story girls don't want to be called きみ is probably in a work situation. It is also sometimes used in a date.

君ーきみーkimi

This is also often used in songs to represent you, especially by female singers, I guess you could class it as poetic language for that reason.

No, you absolutely could not.

おまえ also appears in plenty of enka songs. Always a man singing to a women.