The statement 'she is able to face the milkman with equanimity' implies that

 She is not upset as she has been paying the milkman his dues regularly

 She loses her nerve at the sight of the milkman who always demands his dues

 She manages to keep cool as she has to pay the' milkman only a month's dues

She remains compose and confident, as she knows that she can handle the milkman tactfully