"[Tony] wanted her to be a house mom and be in Dallas, and he wants to go out and play – and not just football," says the source.
Additionally, the source says Simpson and Romo's relationship started to deteriorate toward the end of their time together. "It's been tough for her. Tony had his eyes on everyone but her towards the end," the source tells PEOPLE. "But let's not forget they lasted for a long time and he stuck with her even though the fans didn't like her."
Although Romo has been linked to another woman – Natalie Smith – in reports, Smith's father John, the associate athletic director at Eastern Illinois University, has denied rumors that the pair are an item.
Reps for Romo did not return calls for comment.
In Love with LoveFor Simpson, the breakup has meant letting go of her hopes for a future with the handsome football star. "I think when Jessica gets into a relationship, she thinks she is going to marry him and have babies," the source says. "Every time she ends up with a boy, she is in the zone that it's leading to marriage and babies. That's how she's programmed."
And these feelings were not exclusive to Romo, says the source. "I guarantee when she was with John [Mayer] she thought she was going to marry John," adds the source. "She's in love with love."
Another factor that makes relationships more tricky for Simpson is her family, says the source. "The closeness of her and her family – that takes a toll on the boys," says source. "They are extremely close and when you date her, you date her family."
For now the singer is hunkering down with her parents at their home in Encino. Calif., but the source says: "She will come back stronger. She's working out and she's focusing on herself."