I found my copy of Mia's book, What Falls Away, to refresh myself on the details. According to her book, when Mia discovered the photos of Soon-Yi in Woody's apartment she confronted Soon-Yi, who was home for the weekend, and assaulted her. From page 259: "I pounced on her. I hit her on the side of the face and shoulders. I went into the kitchen, crying. I heard Soon-Yi sobbing...She was my child but I could not help her. I could scarcely look at her. We had become something else to each other. In anger she threatened to kill herself. In anger I told her I hated her. It was a relief from she went back to college."
Soon-Yi left after the assault and she and Mia never saw each other again. (Soon-Yi later claimed in an interview it was a pattern of abuse but Mia said it was a one time thing.)
Mia said she discovered the photos on January 13, 1992 and it was that day she vowed to never let Woody alone with any of her kids. I misremembered that it was related to Dylan's alleged abuse but in her memoir it's because of the Soon-Yi pictures. Mia continued to date Woody after that. She writes that he her took her out for her birthday a month later, on February 13, 1993: "For my birthday Woody gave me three lovely leather-bound volumes of Emily Dickinson's poems, and he took me to dinner at Rao's."
She writes that she told the older kids who knew about the situation with Soon-Yi not to tell anybody, although she reprints in her book a letter she let Moses send to Woody about how he wasn't his father anymore. Mia also says she explained to Dylan, then six, that Daddy couldn't come around anymore and Soon-Yi had left because "Daddy became sort of like a boyfriend to Soon-Yi." She doesn't mention if she told any of the other younger kids. Mia said she and Soon-Yi had no contact anymore after that, aside from one aborted phone call.
Woody and Mia were due to sign their financial and custody agreement on August 6, 1992 and Mia was still letting Woody come and stay at her country home to visit the kids and kinda, sorta continued to date him. On August 4, Mia, Woody and some other people had gone out to dinner to discuss Manhattan Murder Mystery, the new movie Woody and Mia were planning on filming. They came back to the country house and Woody was reading a book to Satchel (now Ronan) and Dylan. Mia and Woody put the kids to bed, but then Mia and Woody got into an argument and Woody left to go back to the city the next morning. It was that day, August 5, that Mia claims a nanny, Alison, notified her that several days earlier she'd witnessed inappropriate conduct between Dylan and Woody. Mia got off the phone, took her camera and interviewed Dylan on video about it, and said she continued to film and interview Dylan "whenever she woke up, in fits and starts" over the next 24 hours. The next day Mia then took Dylan to her doctor, and it was the doctor (a mandated reporter) notified the Connecticut authorities. Mia said she then called Woody's therapist but the therapist cut her off and said she was mandated to report Mia's allegations to the NY authorities.
A few days later on August 13, Woody filed a custody suit against Mia, alleging (among other things) that she was physically abusive to at least one of the children, was overwhelmed by the number of kids with disabilities and provided inadequate care and attention, and was falsely accusing him of abuse against Dylan and Satchel. Mia said she was blindsided and she filed a countersuit, the shit hit the press fan, etc.
I went and looked at the 1992 Maureen Orth article and in it says Woody claims he and Mia had broken up for good in January 1992, though Mia's "friends" told Orth that Mia still thought she and Woody "would spend the rest of their lives together. Even after Dylan's molestation claims, Mia STILL wanted to work with Woody on his movie and called him to ask for the details. He called his lawyer and they cancelled her contract.