I have a 3 1/2 year old and 2 year old, the 3 1/2 year old asks me, " Are you my friend mommy?" whenever she gets in trouble. My response to her is, "Yes, I am your friend, but I am your mommy first."
My own mother is one of my best friends, but it didn't happen until I was out of college and could appreciate the lessons she tought me. She wasn't a harsh disciplinarian by any means, but she taught me about respect for others and respect for myself, to be hard working, and dedicate myself to get what I want in life.
As a parent, it is our responsibility to teach our children right from wrong, respect for themselves and others, to work hard, etc... Friendship will develop as we do those things. You can teach and parent your child, and not be a drill sergeant. You teach through many different forms that include discipline, but are not limited to that, love, support, and nurturing go along way.