Sorry, Mom will never be Dad, no matter how much she loves or respects her child. There is a REASON why it takes two different sexes to produce children.
And it isn't only an example of what men do or what women do which is provided. Children learn about themselves by interacting with their parents. A mother's reaction to flirtatious behavior in a young girl is going to be very different from a father's reaction. Men tend to be better at reining in young male behavior. And the interplay between the mother and father is tremendously important. Children learn how to communicate, they learn compromise.
My aunt lost her husband in an accident when her older daughter was about 4, and her younger daughter was a few months from birth. They lived just around the corner from us and so had male figure in the form of my dad. Neither of these women can sustain ANY type of long term relationship with a man. Their expectations are insane! The older daughter was married for a time (the only man she has ever dated) and nearly pecked her poor husband to death! She wanted to make every decision just like she saw her mama do. The poor guy was not allowed to have an opinion. He got a little tipsy at the wedding reception, and she insisted that he humiliated her and demanded he apologize to us all. We WERE embarassed...for him.