The pair, who won last year's ITV2 series, split up earlier this month after almost a year together.
Now Dani has slammed claims she cheated with Jack following pictures of her kissing former boyfriend Sammy Kimmence this week.
After the snaps were published by newspapers, one of Dani's followers wrote on Twitter: “Everyone was like jack is going to move on the quickest but dani saying she loves him after 2 weeks of splitting with Jack. I say she was texting him while with jack and he found out hence why they split.”
Dani hit back in a now-deleted response: “I’m gonna lose my s***. I don’t text people when I’m with someone. Bore off you no nothing [sic]."
It comes amid claims that Dani's friends and family aren't happy with the apparent new relationship between Dani and her ex.
A source claimed to The Sun newspaper: “Dani’s obviously gone on the rebound after her split with Jack Fincham but everyone thinks Sammy is bad news.
“He’s messed Dani around before and after seeing those pictures of them snogging outside an Essex club, it’s reminded those close to her that she needs to get rid.
Jack and Dani confirmed their split at the start of April.
Dani dismissed claims that the break up was a publicity stunt, coming on the day she launched her own book.
In a now deleted Instagram post, Jack wrote: "There is no easy way to say this and it isn't going to be an easy time but me and Dani are not in a relationship anymore.
"We will always care a lot for each other and have love for each other and I mean that from the bottom of my heart and I wish her nothing but happiness."
He added: "We have some amazing memories together and have been through a lot but sometimes things aren't meant to be and we really did try to make it work but it unfortunately didn't and that is life.
"That's all I have to say, a break up is hard enough as it is for both of us let alone in the public eye so I hope everyone is considerate and understands this."
Dani later had her own say, telling HuffPost UK’s BUILD: “It’s just one of them things, it didn’t work out. There’s going to be a lot of stuff going on about it, but it’ll be fine.
“I wish all the best for Jack, it just didn’t work out.”