Saw this and Lisa says this is why Nancy didn't participate
https://popculture.com/tv-shows/news/facts-of-life-live-nancy-mckeon-absence-explained/?fbclid=IwAR15c4Bd6tiI_XFsVWuXT2yXoPS3J6Ek_y4YL_6JraMFIBMb1plnG3yB1lk
Whelchel said that it wasn't that McKeon didn't want to participate, it's simply that she couldn't due to her recent life circumstances. "Nancy was home and they just recently moved and her kids just got into school, so it was difficult for her to make the trip out," Whelchel said of McKeon's absence.
Luckily, she keeps in touch with her former co-stars. "We have a little group thread we call the 'sisters thread,'" she said. She even joked with Bush when he asked how much each star relates to their characters. Bush asked: "How much is Nancy like Jo?" Whelchel dished, "She is as much like Jo as I am like Blair, which is very little!"