|Family||Rory (father), Isabel (mother), Celia and Cyril (cousins), Norman (brother), Vincent (brother)|
Megan Isabel Green, known as "Megsie" to her family, is the only daughter of Rory and Isabel Green. When her snobbish city cousins, Cyril and Celia Gray arrive at the Green Farm, she and Celia are at each others throats until Nanny McPhee arrives and takes control. Megsie and her brothers, Norman and Vincent, eventually bond with their cousins, especially after Isabel receives a telegram telling her that Rory has been killed in action. While Norman, convinced his father is alive, heads off to London with Nanny McPhee and Cyril to talk to Cyril's father who is very high up in the War Office, Megsie reads a letter from Norman telling her to keep their mother from selling the farm. Megsie and Celia try to delay Isabel for as long as they can. When all seems lost, an enemy pilot accidently drops a bomb in the barley. Megsie's Uncle Phil, who has been trying to convince Isabel to sell the farm after he gambled it away in a casino, becomes hysterical, thinking the bomb is a sign that hit-women, Miss Topsey and Miss Turvey, are coming for him. Norman and Cyril then return and Norman tells Isabel that Phil forged the telegram which announced Rory's death, and he can feel that his father is alive. Phil doesn't try to deny his crime, and Isabel leaves him handcuffed to a rail above the cooker. Megsie then manages to defuse the bomb with some help from Mr. Edelweiss, Nanny McPhee's putty-eating jackdaw. When Nanny McPhee leaves, she gives Isabel and the children her medals with Megsie receiving the medal for Resolve. When Isabel and the children take off after Nanny McPhee, they are reunited with Rory.
"You don't deserve any help, you completely wicked person!" - To Phil after discovering he forged the telegram which said her father was dead.