How does Top Girls by Churchill present its protagonist in both a positive and negative light?

The play Top Girls by Caryl Churchill investigates what constitutes female success and paints a nuanced portrait of its flawed protagonist, Marlene, an ambitious business woman who leaves her child in the care of her sister in order to pursue her career. Marlene's choices are neither sanitized nor demonized by the play. Instead, she, along with her own conception of what "success" entails, are shown in both a positive and negative light depending on context.
The play opens with Marlene hosting a dinner party at a restaurant for various famous real and fictional women from throughout history to celebrate a recent promotion at work. This scene places Marlene and her ambitions in historical context and includes her in a pantheon of women who have achieved great things in spite of the patriarchal society that attempted to keep them down. In this scene, the portrayal of Marlene is overwhelmingly positive. Marlene's promotion is presented here, at least in Marlene's own mind, as being on the level of Pope Joan pretending to be a man and ascending to the highest role in the Catholic Church or explorer Isabella Bird's many discoveries. Though none of the women present can agree on what constitutes female success or the best way to achieve it, the play embraces the dialectical nature of their conversation. Marlene's way—climbing the corporate ladder—is not the only way, but it is no worse than any other.
The following scenes of the play are written in a decidedly more realist mode, with characters from the present day only. The difference between the positive portrayal of Marlene in act 1, scene 1—which is a celebration of female empowerment—and the grittier, negative portrayal of her in the scenes that follow is partially due to this tonal shift.
In the Top Girls office, the audience is privy to Marlene's hard, no-nonsense business persona. Here, she is cold and conservative. The point of the Top Girls Agency is to help women advance in their careers, but it seems that Marlene's philosophy in doing this is to become more traditionally masculine, embracing competition and toughness. She values individualism and works toward the advancement of singular ambitious women, rather than liberation of the group as a whole.
It is perhaps in the scene between Marlene and Joyce, accompanied by the revelation that Marlene is Angie's mother, that Marlene's portrayal becomes most complex. Though the audience can understand her values and the decisions she has made, her strained relationship with her sister and her lack of a relationship with her own daughter drive home the point that she has chosen her own advancement over all else. Though she tries to help her sister financially, money, which Marlene has sacrificed so much to gain, is not enough to restore her familial relationship.