Vanessa Trump Discovered 'Sexy Texts' from Aubrey O’Day While Donald Jr. Showered: Source

Donald Trump Jr.‘s alleged affair with former Celebrity Apprentice contestant Aubrey O’Day came to an abrupt end in 2012 when his wife, Vanessa, discovered “sexy” text messages between the pair.

A source who worked with Celebrity Apprentice — where Trump Jr. and O’Day first connected when she was a contestant and he was an adviser on the show — tells PEOPLE that President Trump’s eldest son was in the shower and his phone was on the bedside table when “sexy texts” came through from O’Day.

“This is how Vanessa found out and the affair ended,” says the source familiar with the situation.

“To Don Jr. [the affair] was very exciting,” the insider adds. “Aubrey was very, very into Don. He liked her but she was definitely more keen on him.”

Last Thursday, Page Six broke the news that Vanessa had filed for divorce from Trump Jr. after more than 12 years of marriage. The outlet was also the first to report on Trump Jr.’s alleged fling with O’Day, a former singer in the girl group Danity Kane.

Although the couple went through a rocky time after Vanessa uncovered the alleged affair, the source tells PEOPLE that “everything seemed to be patched after that as Vanessa had more kids afterwards.” (Trump Jr. and Vanessa share five children together: Kai Madison, 10, Donald III, 9, Tristan, 6, Spencer, 5, and Chloe, 3.)

“They were a very sweet couple and Vanessa was lovely,” the source says. “Aubrey always seemed really stuck-up.”

A spokesperson for Trump Jr. did not respond to PEOPLE’s request for comment, and O’Day’s manager, Steven Grossman, told PEOPLE that she is not commenting at this time.

But on election night in November 2016, O’Day tweeted that “my story I didn’t tell is worth millions now.”

RELATED VIDEO: What Went Wrong Between Vanessa and Donald Trump Jr: He Grew ‘Distant, Angry;’ She Felt Stifled

Of all the stresses that reportedly pulled at Vanessa and Trump Jr.’s marriage — from his racy tweets to a former model, to the alleged affair with O’Day, to his cheapskate approach to Vanessa’s spending — friends tell PEOPLE in this week’s new issue that the strain between husband and wife was nothing new.

The couple had been living “separate lives” for a while, says a source who socializes with them. “Even before all this Trump presidency stuff started, they weren’t good and their marriage was strained.”