Margaret "Maggie" Duval is Soraya Duval’s smart aleck mother and Marion's best friend. Maggie ran a business in town called Maggie's Tack and Feed. In Season 7, Maggie sells the diner to live in London with Soraya. Lou doesn't want to let anyone to turn Maggie's into a hotshot fast food joint so she ends up buying it. Many people hang out at Maggie's. Lou opened up a second Maggie's Tack and Feed in New York.
Maggie, the owner of Maggie's Diner, she overhears Val Stanton talking about Heartland and how they are a lie and without Marion the business will fail. When Jack comes in a few days later she informs him of what Val has been saying. (After the Storm) Maggie is seen working at the Diner when the Briar Ridge commercial plays. (The Best Laid Plans) Maggie is working at the Diner with Jack and Lisa reading the newspaper article about Gallant Prince. Maggie suggests Amy work with him. She's later in the Diner with Soraya and Amy reading the article about how the reputation of Heartland hangs on Amy's work with Prince. (Out of the Darkness) Maggie's working at The Diner when Soraya tells her about Ben inviting her to groom for him at a show next weekend. (Ghost from the Past) Maggie sells Lisa some fishing gear from Maggie's. When she sees Lisa is back she tells her she thought she was back to get a refund but instead she says she had a great time with Jack. (Thicker Than Water) Maggie talks to Lou about the upcoming jumping show and she tells her that Soraya isn't competing since she failed biology. The night of the formal and reunion, Amy, Lou,Scott and Ty are in Maggie's when she gets a call about the barn fire. She later helps other friends and neighbours re-build the barn at Heartland. (Rising from Ashes)
Maggie is annoyed that Soraya quit on Lou, she tells Soraya she will sponsor her instead. (Sweetheart of the Rodeo) Lisa vents to Maggie about the situation with Lou and how it's affecting her relationship with Jack. (Seismic Shifts)