From the moment Justin Baldoni announced in 2019 that he was adapting the best-selling book It Ends With Us into a film, there was a widespread frenzy.

There are few books in recent years that have become as big a cultural phenomenon as Colleen Hoover’s novel – it has sold 20m copies and became an internet sensation on TikTok with more than one billion tags on the app.

When Blake Lively, who rose to fame in the 2000s playing Serena van der Woodsen in Gossip Girl, was cast as the main character, fans became even more excited, describing her as the perfect choice to play Lily Bloom, a young woman who grew up witnessing domestic abuse and winds up in the same position years later.

Lily, a florist in Boston, navigates a complicated love triangle between her charming but abusive boyfriend Ryle Kincaid – played by Jane the Virgin’s Justin Baldoni – and her compassionate first love, Atlas Corrigan (Brandon Sklenar).

Released at the beginning of August, the film became a box office success bringing in more than $350m (£280m) globally.

But despite its financial success, everything wasn’t running so smoothly behind the scenes. Rumours of a feud between Baldoni and Lively began swirling before the film was even released.

Last week, Lively filed a legal complaint against her co-star, accusing him of sexual harassment and starting a smear campaign against her, something Baldoni strongly denies. Here is the story so far:

For a film about domestic abuse, the press tour for It Ends With Us was probably not what you would have expected. There were pink carpets, flowers galore and the promotion of Lively’s new haircare brand and her husband’s gin company.

Instead of advocacy on the red carpet, Lively highlighted fashion and florals.

At the London premiere, press were told to keep questions “fun and light-hearted” with one event organiser telling me to “steer away from questions on domestic abuse”.

One of her remarks made at the New York premiere – “you are so much more than just a survivor or just a victim” – sparked backlash on social media.

Domestic abuse survivor Ashley Paige criticised Ms Lively’s language and told the BBC that her own trauma “shaped my identity”.

Lively was also criticised for her comments in another clumsy promotional tour video where she said: “Grab your friends, wear your florals and head out to see it.”

Ms Paige accused Lively of promoting the film like it’s “the sequel to Barbie”.

Alongside the press tour being described as “tone-deaf”, people started asking questions about why the Lively and Baldoni weren’t photographed on the red carpet together at the film’s New York premiere on 6 August.

The pair also did no interviews together during the press tour and at the London premiere, which Baldoni didn’t attend, I was warned by Lively’s team to not “ask any questions about Justin”.

Internet sleuths also spotted that cast members including Lively and author Hoover did not follow Baldoni on social media.

Neither Lively or Baldoni addressed rumours of a feud during the press tour and the only reference to each other was Baldoni telling Today that his co-star was a “dynamic creative”.

“She had her hands in every part of this production, and everything she touched made [it] better,” he said about the 37-year-old.

While the film was a box office success, it received mixed reviews from critics with some saying it romanticised domestic abuse.

There was a two-star review from The Telegraph’s Tim Robey, who called it a “queasy drama” that “repackages domestic violence as slick romance”.

He suggested the film “splices abuse and glossy courtship in the big city to deeply dubious effects”.

The movie also sparked a debate on TikTok, with some saying that it’s not clear from the trailer that this story is about an abusive relationship and rather it appears to be telling a love story.

Based on this misconception, some people said they found the film traumatic as they didn’t know it contained scenes of domestic abuse.

During the film’s press tour, Baldoni hired a crisis manager, Melissa Nathan, whose previous clients include Johnny Depp and Drake.

Shortly after the press tour, Lively faced a barrage of criticism on social media relating to her comments on that tour as well as from old interviews.

One of the interviews to resurface was one shared by a Norwegian journalist, Kjersti Flaa, who posted a video on YouTube of her interviewing Lively in 2016. It was titled “The Blake Lively interview that made me want to quit my job.”

Actor Brandon Sklenar, who plays Atlas in the film, defended Lively and said in a post on Instagram that people had been “vilifying” the women involved in the film online.

He said it was “disheartening to see the amount of negativity being projected” and that someone close to him who had experienced a relationship similar to Lily’s had credited the film with “saving her life”.

Four months after the film’s launch, Lively filed a legal complaint against Mr Baldoni in which she accused him of sexual harassment.

The complaint also listed Wayfarer Studios, Mr Baldoni’s production company which produced It Ends With Us, as a defendant.

The legal filing accuses Mr Baldoni and Wayfarer CEO Jamey Heath of “repeated sexual harassment and other disturbing behaviour”. Some other female cast and crew had also spoken up about their conduct, the filing alleges.

It also alleges that Ms Lively, Mr Baldoni and other people involved in the development of the film attended a meeting in January to address “the hostile work environment” on set. Her husband, actor Ryan Reynolds, attended the meeting alongside her, according to the complaint.

At the meeting, attendees agreed to a list of demands, including Mr Baldoni and Mr Heath making “no more descriptions of their own genitalia”, requiring an intimacy coordinator on set at all times when Ms Lively was in scenes with Mr Baldoni and no “friends” of the producers and directors being on set during scenes when Ms Lively was in a state of nudity.

The list of demands also implied that Mr Baldoni had asked Ms Lively’s trainer how much she weighed and alleged that Mr Baldoni and Mr Heath had spoken about their “pornography addiction” to Ms Lively.

In the filing, Ms Lively also alleges that Mr Baldoni and his team attacked her public image after the meeting.

She accuses him of orchestrating a plan to “destroy” her reputation in the press and online, including hiring a crisis manager who led a “sophisticated, coordinated, and well-financed retaliation plan” against her and used a “digital army” to post social media content that seemed authentic.

“To safeguard against the risk of Ms Lively ever revealing the truth about Mr Baldoni, the Baldoni-Wayfarer team created, planted, amplified, and boosted content designed to eviscerate Ms Lively’s credibility,” her team wrote in the filing.

It adds: “They engaged in the same techniques to bolster Mr Baldoni’s credibility and suppress any negative content about him.”

In the filing, Ms Lively says that this had led to “substantial harm” that affected “all aspects” of her life.

Mr Baldoni’s legal team told the BBC the allegations are “categorically false” and said they hired a crisis manager because Ms Lively had threatened to derail the film unless her demands were met.

Responding to the legal complaint, Mr Baldoni’s lawyer, Bryan Freedman, said on Saturday: “It is shameful that Ms Lively and her representatives would make such serious and categorically false accusations against Mr Baldoni, Wayfarer Studios and its representatives.”

Mr Freedman accused Ms Lively of making numerous demands and threats, including “threatening to not show up to set, threatening to not promote the film”, which would end up “ultimately leading to its demise during release, if her demands were not met”.

Hollywood stars including America Ferrera, Amber Tamblyn and Alexis Bledel have publicly backed Blake Lively after she filed her complaint.

Ferrera, Tamblyn and Bledel, who starred with Lively in 2005 film The Sisterhood of the Traveling Pants, issued a joint statement on Instagram, on Sunday saying they “stand with her in solidarity”.

“Throughout the filming of It Ends with Us, we saw her summon the courage to ask for a safe workplace for herself and colleagues on set, and we are appalled to read the evidence of a premeditated and vindictive effort that ensued to discredit her voice,” they wrote.

Colleen Hoover, the author of It Ends With Us, also showed her support, describing Ms Lively as “honest, kind, supportive and patient”.

Additional reporting by Grace Dean.