THEY wanted a “no-holds-barred” tell-all  about her “BLUE BLOODS” costars and quickie nups to hunky Bradley Cooper –  but JENNIFER refuses to squeal. WHY???

JENNIFER ESPOSITO was pushed by publishers to pen a blistering tell-all about her “Blue Bloods” co-stars and baffling four-month marriage to Bradley Cooper – but instead she decided to help others afflicted with the serious health problem that led to her being dumped by the hit CBS cop drama.

Sources tell The ENQUIRER that the 40-year-old beauty has taken pen to paper to talk about her struggle with Celiac disease rather than a book about her disappointment in co-stars Tom Selleck and Donnie Wahlberg and details about her union to Cooper.

“Jennifer was under a lot of pressure from publishers to reveal secrets from her personal life, but she’s always taken the high road,” a friend told The ENQUIRER.

The actress enjoyed a robust 20-year career in TV and movies before signing on in 2010 to play Det. Jackie Curatola on “Blue Bloods,” which revolves around a family of New York City cops.

But just a year later, she was diagnosed with Celiac disease, an autoimmune disorder that causes intense digestive distress and pain. The ailment affects some 2.2 million Americans and is triggered by the gluten found in grains such as wheat, rye and barley. It can be deadly if left untreated.

As Jennifer struggled with the agonizing disease during her second season on the show, she was put on unpaid leave. But since she was still under contract, she was not allowed to seek other TV work.

What hurt even more, say sources, was the relative silence from her co-stars Selleck and Wahlberg, who she believed could have backed her more strongly in her war with CBS. She eventually left the show amid her bitter dispute with show executives.

“Despite that, Jennifer won’t call them out in her book,” said an insider.

She’ll also refrain from discussing why her 2006 marriage to 38-year-old hunk Cooper crumbled so quickly.

Explained her friend: “Jennifer believes her story lies in how she battled her disease, not how the actors in her life let her down.”