If that doesn’t happen here, I can’t think of a valid reason to keep her over someone willing to do reforms.

Politically this is gift to Mamdani that she holds the position:

• He didn’t appoint her, so he has low risk of keeping her
• It can make him look apollitical that he is willing to keep on staff from the previous administration and not act purely on political grounds
• He earns political points, influence, and support from the rich family because he did not remove her
• She knows she has a political target on her back, so she’s incentivized to keep him happy carrying out his mandates
• When NYPD has a scandal, he can immediately point to her, and her leadership, and fire/prosecute her for it
• When the removal finally does happen he’ll score points with his base for removing yet another relic of the Adams administration and be able to appoint a reformer