why has Mrs.Flowers remained for Angelou "The measure of what a human being can be"?

This is similar to your last question on this. Maya finds Ms. Flowers a unique role model. She is a black woman who refuses to bend to the stereotypes placed upon black women at the time. Maya finds Ms. Flowers to be intelligent, self-aware, proud and sincere.

Ms. Flowers instills a sense of pride both in Maya and in her identity as a black African American woman. To Ms. Flowers, academics, afternoon tee and literature were not merely white past times. She showed Maya that intellectual and emotional enlightenment were her right as a human being.

Maya aspires to be like her one day. Like Ms. Flowers, Maya wants to hold her head high not simply as a black woman but a proud and intelligent human being.