Caroline Dubois labelled Alycia Baumgardner a coward after the pair were involved in a heated confrontation at ringside on Saturday night.
The transatlantic rivals have been heavily-linked to a potential super-fight as Baumgardner prepares to step into the same division as Dubois when she challenges Elif Nur Turhan for the IBF lightweight world title on November 8.
Dubois was approached by a spectating Baumgardner at the ropes in the immediate aftermath of her in Birmingham, a tug of war at the microphone and fierce war of words further fuelling their growing feud.
The Londoner later criticised Baumgardner's absence in her post-fight press conference.
"I'm surprised she isn't there. I think she's a coward," she said. "I wish she was here so I could say it to her face. I really do.
"I think she's a coward. I think she's a coward because she isn't here today. She should have come to the press conference. This is the biggest fight in women's boxing."
Baumgardner described the performance as "lacklustre" and insisted Dubois would need to "tighten up" were she to have a chance of beating the former undisputed world champion.
Dubois hit back by questioning Baumgardner's failure to secure fights against Katie Taylor and Claressa Shields, while explaining how she was "already better" than her at the age of 25.
"She's tried as hard as she can to dismiss me and make it seem like I'm not on her level, but I am," Dubois continued.
"I'm the world champion, and she's moving up to my division. Yeah, I think this is the biggest fight in women's boxing.
"I think it will be a great fight, and I hope that she wins against Elif [Nur Turhan], but you never know.
"Maybe it's Elif who wins, and it'll be me and her facing off, so let's not try and write off Elif."
Stephanie Han is another possible option for Dubois having just retained her WBA lightweight title in a majority decision win over Holly Holm.
"Nakisa [MVP co-founder Nakisa Bidarian] flew me out earlier this year to watch Stephanie fight against Holly Holm," said Dubois.
"I went to the press conference afterwards. I wasn't afraid to come to the press conference.
"I called her out openly there and then, and she promised me we would do it, that it is a fight that's going to happen, and I intend to hold her to that. I want to fight Stephanie."
Speaking to Your Site, MVP founder Jake Paul said they were "100 per cent ready to go when they want to sign the contracts" with regards to a fight between Dubois and Baumgardner.
It comes after Claressa Shields accused Baumgardner of being "scared" of Dubois, to which the American replied by calling her counterpart "jealous".
"Alycia is not scared of anyone, I know it's going to happen, she has to get through November 8 and then we can have those discussions," said Paul.
"I think it's funny when fans or critics say certain people are scared of somebody - they aren't scared, it's what they do for a living."
