“Castle” lead star Stana Katic is leaving the show allegedly because of her love interest in the series – Nathan Fillion.

The actress and Fillion have played onscreen couple Detective Kate Beckett and Richard Castle. Us Weekly reported that just like the characters they played, the couple has even  gone to a counselling.

“Stana would cry on set because Nathan was such a bully to her,” one source told Us Weekly. Another insider added: “Stana would go in her dressing room and cry. A lot of people who work on the show don’t like Nathan. It’s not just her.”

“The friction was very evident. Nathan has been nasty to Stana for a long time. Stana was a pro, just wanted to get in there and do her job,” a source added.

Last year, Katic opened up about working with Nathan Fillion while attending the People’s Choice Awards, Us Weekly noted. The actress said at the time: “I think it all starts with [the] writing… And after that, hopefully you are able to bounce a ball back and forth with your partner. And Nathan and I manage to bounce that ball back and forth, I think, well. I hope. People seem to like it.”

Mail Online wrote that there were also speculations that the tension between the two stars had become so bad that they no longer spoke to each other except when the cameras are rolling.

However, Deadline reported that ABC chose not to renew Katic’s contract because of financial reason.

Deadline further claimed that those working behind the scenes on the drama began negotiations with Fillion “for a new deal.” However, Katic was  “never approached” to renew her contract “and was not offered an opportunity to continue on the show.”

The actress is due to leave the ABC crime procedural drama after the current eighth season.

In a statement, Katic said, “Rather than distract from what was an amazing experience, I would just like to say that I’m very grateful to ABC for giving me the opportunity to be a part of a much-beloved show.”

She also took to Twitter and thanked her supporters. “To the fans: thank you for your support. I love you,” she wrote.

Meanwhile, Fillion broke his silence about Katic’s exit on the show and posted a message on his Twitter account.