Her exit follows that of First Assistant D.A. Joseph E. McGettigan, Williams' second-in-command, who left the office on an open-ended medical leave June 6.
McGettigan, in a letter published in the Daily News, denied his departure was due to friction with Williams, which the paper reported based on D.A. office sources.
In May, the paper reported that Assistant District Attorney Jennifer Mitrick had been yanked from prosecuting two men accused of attempting to murder an alleged drug dealer after it was discovered that she had dated the victim, who survived a bullet to the head.
Michael Wilson, the alleged Rastafarian drug dealer who had been involved with Mitrick, is facing drug and gun charges and is scheduled to be tried in September, according to court records.
Mitrick is still employed at the D.A.'s office.
In her decade-and-a-half as a prosecutor, Feeney's cases ran the gamut from spine-chillers to head-scratchers.
There was the case of Christopher Kitcherman of Kensington, convicted in 2007 of dismembering his father and putting body parts in a freezer.
Then there was the case of Aaron Bell of West Philadelphia, convicted in 2002 of robbing the KFC where he worked and then showing up for work three days after the robbery.
"It's just like you basically have to ask yourself, 'What was he thinking?' " Feeney said after the trial.