Looks like Dorinda Medley might need Andy Cohen to mediate this fight with her neighbor ... 'cause the neighbor's firing back over the housewife’s lawsuit!

According to court docs obtained by TMZ, Dorinda's neighbor is denying claims that she's encroaching on "The Real Housewives of New York City" alum's famed Massachusetts estate, Blue Stone Manor.

The neighbor argues that everywhere she’s accused of encroaching is still within the bounds of her own property, and insists she's already moved any possible encroachments.

What's more is she's saying Dorinda’s full of crap ... the neighbor claims she never received repeated demands about the alleged encroachments.

As we previously reported, Dorinda believes her neighbor's new shed, fence, and driveway are encroaching on her posh property.

Maybe Bravo wants to grab a camera crew ... 'cause this is starting to get good.