Casey, 31, sensationally revealed her secret relationship with 24-year-old Jonathan this week, admitting she felt used by the England rugby player.
According to reports, 22-year-old Eloise, who has been with Jonathan for seven years, has now ended things with him for good.
A source told The Sun: “It’s not been a good week for him, dumped out of the World Cup and now dumped by his girlfriend. She feels humiliated that she was dragged into this.”
Former Celebrity Big Brother star Casey told how Jonathan sent her a barrage of messages before they met up in a hotel for sex.
But Casey was left crushed when the sportsman told her he had a girlfriend broke things off with.
She said: “I’m gutted. He just used me for fun. There was never any mention of a girlfriend. Even after we slept together he continued to treat me really well.
“He stayed in bed and we had cuddles. He texted me as soon as he left to say what a nice night he’d had. I never saw it coming.”
Casey insisted that, if they were going to continue seeing each other, he would have to break things off with Eloise.
She added: “He’s clearly just an immature 24-year-old.”