Melody Shari Says Ex Martell Holt Hasn't Changed, Didn't Know About New GF

"Love and Marriage: Huntsville" star Melody Shari doesn't think her ex-husband's had enough time to become a better guy before jumping to his new boo, Sheree Whitfield -- and says the proof is online for all to see.

Melody told us, in her opinion, Martell Holt's really gotta work on himself, but she fears he's still the same untrustworthy guy she married back in 2008.

As we reported, a shirtless Martell and 'RHOA' star Sheree were spotted taking selfies together, and sources in the know tell us they've been dating for a few months.

Melody says she found out about their relationship the same way everyone else did ... the Internet, and that's also how she found out her kids already met Sheree.

She's not shocked, though, as she reminded us about how her kids were slyly introduced to a child Martell previously had with another woman.

Martell has been very vocal about boundaries with their kids after they split last year -- but Melody says it's the same old, same old with him and adds, she'd handle this totally differently ... especially with her kids involved.

Melody's been working on herself since the split, learning she's OK healing alone while focusing on her kids and businesses.

Meanwhile, we got Sheree in Sandy Springs, GA and she told us she met Martell through mutual friends, and is already introducing him to some of her pals and family members.