The celebrities — each paired with the Italian on the dance show — first made contact on social media before getting together in-person on Thursday to “compare notes”.
Sources said “tears were shed” as they offered one another support over their experiences with the “intense perfectionist” Gio.
Sherlock star Amanda, 52, quit the show in October citing medical reasons and has since revealed that she has been diagnosed with mild post-traumatic stress disorder.
Good Morning Britain presenter Ranvir, 46, who was partnered with 33-year-old Giovanni in 2020, complained about him to producers during her stint on the series.
Former Love Island presenter Laura, 38, meanwhile, said she “cried every day” and felt “uncomfortable” while training with him when they were paired up in 2016.
A source said: “All three had difficult experiences with Giovanni, who is well known to be intense during training. They met in person to share their experiences.
“Their meeting was emotional but heart-warming. They now know they are there to support each other after their tough times with Giovanni. Tears were shed.
“There is every possibility all three could take it further and formally complain to the BBC, but for now they’re comforting each other.”
The source added: “Only a handful of people will understand what it’s like to be trained by Giovanni and in the industry he is regarded as a ‘perfectionist’.
“He’s been known to row with many of his partners.”
Mr Selfridge star Amanda is lining up top lawyer Persephone Bridgman Baker for help to prepare a legal letter to the BBC to aid her in retrieving footage of her rehearsals with Giovanni.
Amanda, who has two kids with actor ex Martin Freeman, 52, has told how she received death threats when she revealed her PTSD diagnosis after quitting Strictly.
She said: “I told a few people about that, in the utmost confidence, among other things that were happening in my life . . . both professionally and personally.
“I’m very sorry that people felt the need to send me death threats, threaten my children and bring up my past, healthy relationship with an ex-partner as an indicator of my current mental health. I wish those people well.”
Ranvir also flagged an issue during training with Giovanni, who has been on the show since 2015, and said that she was unhappy.
And telly host Laura wrote: “I’m still not ready to talk in-depth about my experience on the show. I was placed with a dance partner I was extremely uncomfortable with. I cried every day. And I really was broken, both mentally and physically, by the end.”
In another interview, she said: “What I didn’t like was being removed from everybody and having to spend 12 hours a day with this one person.
I’m still not ready to talk in depth about my experience on the show. I was placed with a dance partner I was extremely uncomfortable with
Laura Whitmore
“It did not become about the dancing. I just wanted to dance. I did not want to play the game of doing red carpets with your dance partner and stuff like that.”
The BBC said in January it would not be conducting an investigation into Giovanni’s behaviour with Amanda.
A spokesman said: “There is a constant dialogue between the senior production team and contestants to ensure any concerns are addressed swiftly.”
The source told The Sun on Sunday: “There is some shock that the BBC appears to be doing nothing. Like Amanda, Ranvir also flagged an issue during training with Giovanni and said she was unhappy.
“While Laura has been vocal about how she found her time on the series distressing.
“Amanda is lining up a well-known lawyer to help her gain access to the rehearsal tapes of her and Giovanni with the aim of reviewing them.”
Tomorrow, BBC1 will air the first episode of Giovanni’s new travel series with Strictly judge Anton Du Beke — called Anton & Giovanni’s Adventures in Spain.
Giovanni is currently touring with his stage show and last month he revealed on BBC local radio that he would be returning to the Strictly for one final series.
A Strictly spokesman said they would make in announcement in “due course.”
Sicilian-born Giovanni, who won Strictly in 2021 with EastEnders actress Rose Ayling-Ellis, 29, has had a series of issues with some of his previous dance partners.
Former Steps singer Faye Tozer, 48, is understood to have clashed with him in 2018, while TV personality Richie Anderson, 36, unfollowed him on Instagram.
A source close to the pro dancer said: “Gio finds some of these allegations deeply unfair and offensive. He believes he’s done nothing wrong, and simply wants to get the best out of his partners.”
The BBC declined to comment.