DeSantis then quotes from the lyrics to Jackson's hit "Man in the Mirror," which includes the verse: "I'm starting with the man in the mirror; I'm asking him to change his ways."
It's not known whether Mill is a Jackson fan, and DeSantis conceded she and the 27-year-old hip hop artist "share different types of music tastes."
Nevertheless, DeSantis wrote, music has the "power and ability to transcend cultures, language, race, and gender."
For Philadelphia-born Williams, Monday was the 17th day of the sentence for violating probation on a 2009 gun and drug conviction.
Last Wednesday, Williams' lawyer filed a motion for early parole, arguing that prison is financially damaging his burgeoning concert and recording career, including the Sept. 9 release of his next album, Dreams Worth More Than Money.
Judge Genece E. Brinkley, who sentenced Williams on July 11, has not set a hearing on Williams' parole motion or DeSantis' response, and has told the parties a hearing isn't likely before Labor Day.
Since being sent to Curran-Fromhold Correctional Facility, Williams has missed at least two concert dates, and his recording company has warned that his inability to promote his career could imperil his next album.
Brinkley accused Williams of "thumbing his nose" at probation, booking concerts against her orders, and failing to comply with its terms.
Regardless of whether Williams hears her musical message, DeSantis wrote that his warnings of financial disaster were overblown.
Williams "will develop more street cred while in custody," DeSantis wrote, "and when he is eventually paroled, it will create a frenzy/media blitz in the entertainment world and he will recoup any monetary losses he has sustained while in custody."