The source added that the Great Gatsby star barely spoke to the 18-year-old model.
After news broke on Tuesday that Maguire was separating from Meyer, a source told ET that the couple had actually called it quits months ago but it "was not over anything specific or dramatic." Rather, the two "grew apart and realized they both had changed as people."
They also released a joint statement to ET, saying that "after much soul searching and consideration," they had decided to "separate as a couple."
Another source told ET that Maguire and Meyer are still good friends, and are "very supportive of each other and are committed to their kids," 9-year-old daughter Ruby, and 7-year-old son Otis.
The two certainly appeared amicable when they attended an event in Hollywood together on Oct. 6. Maguire and Meyer posed for pics at the Roe Caviar 2016 Harvest at the home of Jonas Tahlin, CEO of Absolut Elyx, and were joined by Courteney Cox, Kate Hudson and Rachel Zoe. "The two seemed totally normal and fine at the event," an onlooker at the event told ET, adding that there weren't any hints of trouble in the relationship.