"Yes, William, represent the company, don't worry about the family. Show your true colors. I'm sure there's no one else in the company to do that."
Millie was once married to Jim Morse, but the two had a rather nasty falling out and divorce, primarily because of Millie's reluctance to bear Jim any children (something she would later come to regret). The divorce was so bitter, Millie changed her husband's last name back to her maiden name. However, over time, the two put aside their differences, and became friends, getting on with their lives.
While Darren was visiting his birth family in Lawndale, Millie met someone new in London while recovering from the deaths of her brother and sister-in-law, a charming British gentleman named Edward White, who claimed he was working in a Danish brokerage firm, Mikkelson Industries. In reality, Edward was secretly working for a British tabloid, the Weekly Blabber, for his boss, one James Bowman. White's job was to get as much dirt as he could on Darren Appleton and his family for the tabloid.
Jim Morse paid a visit to the mansion while Darren's birth family, Jane, and the Fashion Club were visiting themselves, wanting to meet them all. In reality, however, Jim wanted to see Millie again because he still had feelings for her--and to scope out Edward White and his motives. Immediately, the two men began an acrimonious competition for Millie's hand, all the while pretending to get along with one another. Millie, not fooled, had to play peacemaker between the two several times, taking Edward's side more often than not.
In the end, more out of hoping he could find something, anything to break Millie and Edward up, Jim had secretly hired Gerald Woo to dig up a little dirt of Jim's own on Edward, which Woo did, discovering Edward's connection to the tabloid. Edward was subsequently arrested.
Millie, stunned and angry over Edward's clandestine activities (as well as Jim's--she apologized to him via a letter later), promptly left the mansion later that night, very upset, wanting to get away for a time. As of the moment, it's not known where she is, and there is a strong possibility that Millie is now pregnant with Edward's child.
Millie was very close to Darren, considering him as something like a son, since she herself had no children (Darren was as close to one as she wanted at the time). In fact, it could be argued that she was something of a mother figure to him when Lucille wasn't around. At first, Millie actually feared that the Morgendorffers would occupy so much of Darren's attention, that she thought they could "take him away" from her. This was later clearly refuted by Helen Morgendorffer, who proposed that Millie be "adopted" by them as a "new" aunt to Daria and Quinn, becoming a permanent part of the family. This obviously overwhelmed and delighted Millie, who eagerly accepted. In the time the Morgendorffers stayed at the mansion, Millie and Helen have become close.
Revelations (Chapter 1)
Original Character Profile from Mike Yamiolkoski's Daria Online Character Database, now offline.