Battle of the exes! Nikki Bella is working on a memoir about her life, and one person that’s scared of what she will reveal is her ex-fiancé John Cena, a source exclusively told In Touch.

“John heard that Nikki is writing a book, and he’s clearly doing some damage control. That’s why he’s tweeting,” an insider revealed. “There’s clearly still some bitterness between them. Nikki and her sister, Brie Bella, had a book deal. I don’t know where that stands now, but Nikki now has a lot more to say. She’s now working on a new book.”

On Monday, May 6, the 42-year-old wrote a cryptic message on Twitter seemingly about his previous relationship with the Total Bellas star. “Beware those who think you owe them happiness at the expense of your own well-being,” he said.

Nikki Bella Wearing a Black Outfit With John Cena
Axelle/Bauer-Griffin / Getty Images

Then, the following day, the brunette beauty, 35, tweeted a message that seemingly responded to her ex. “When you don’t give him what he wants, he will delete you, silence you, manipulate you, do what he can to destroy you, but turn that hurt into strength,” she wrote on May 7. “Take the high road and prevail! Happiness can’t be bought, it is priceless. It’s your true secret weapon. N.”

Of course, Nikki’s followers rallied around her and pointed out why their relationship never worked out. One person wrote, “Just remember John’s strict voice calling all the shots, etc., kids, house rules, etc.! You’re a free spirit, Nikki! You don’t ever need that in your life again,” while another echoed, “He didn’t know what he had and treated you like an object and not his life partner. He can kick rocks. Nikki, move on and move forward.”

So, what will the California native divulge? “Nikki has always wanted to empower women and her fans, so it will be part memoir and part inspirational,” the source continued. “How could she not write about such a crucial life event — meaning John and her broken engagement — which wasn’t easy. But in the end, it did make her stronger. John heard about the book, and he’s trying to get ahead of it.”

After six years together, the Trainwreck alum and the retired professional wrestler called it quits in July 2018. “After I called off the engagement, we tried to work on our relationship to get back to where it was in order to move forward with our wedding,” she told Us Weekly at the time. “After much time and soul-searching alone, and together, we have decided to officially part ways. I had a beautiful and loving six-year relationship with a wonderful man. I have the utmost respect for John, but I know this is what’s best for me.”

Even though the former flames have moved on — Nikki is dating her former Dancing With the Stars partner, Artem Chigvintsev, while the Massachusetts native was spotted out on a date with Shay Shariatzadeh — it doesn’t mean that model doesn’t think about John.

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When Nikki first saw pictures of John with his new lady, she discussed her reaction. “He’s one of the people, besides you, Brie, who’s made me an amazing person,” she said on “The Bellas Podcast” on April 24. “But because of how sad and how much I hurt him, when I saw the big smile on his face, I felt happy for him. I am very happy for him. As long as John is happy, I’m happy.”

Welp, it seems like these two won’t be on good terms for much longer.

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