A source told The Sun that Rodriguez, 35, got tired of the 21-year-old British model's hard-partying lifestyle.
"Michelle got tired of Cara constantly being pictured with other female celebs," the source said. "Michelle isn't as interested in being in the limelight. She thinks they have different priorities."
The couple's whirlwind romance went public in January, when they were photographed making out at a Knicks game in New York City.
Rodriguez confirmed their relationship in February, reportedly telling the Daily Mirror that she and Delevingne "have the best time together."