Sources told the newspaper that Davy, the royal's girlfriend for more than three years, checked his cell phone after she overheard him having a hushed conversation with a woman.
"She stole a look at his phone and found the text messages. Chelsy was furious. She then confronted Harry and they had a blazing row," the insider said.
Davy reportedly told Harry in a series of emotional phone calls last week that they needed a "cooling off" period.
But friends said Davy is frustrated by his lack of commitment and hard-partying lifestyle, especially since she only recently moved to England from her native Zimbabwe to be closer to him.