James Kennedy and Ally Lewber are putting up a united front ... we've learned the Bravo couple has no plans to split following the "Vanderpump Rules" star's domestic violence arrest.

Sources familiar with the situation tell TMZ ... the DJ and his astrologer girlfriend are sticking together in the wake of the controversy, with Ally choosing to stand by James in this situation.

We're told Ally and James did have an argument Tuesday evening, after they returned home from Kathy Hilton's holiday party. Sources say a neighbor caught wind of the spat, "overreacted" and called 911.

We're told the whole thing was a misunderstanding.

Sources who spent time with Ally on Wednesday evening, when she stepped out for Windsor’s New Year’s Eve celebration at Short Stories Hotel in Los Angeles, tell TMZ ... James' GF didn't bring up his arrest and seemed to be in good spirits.

In short, we're told Ally didn't act like anything had happened the night before.

TMZ broke the story ... the reality TV star was arrested for misdemeanor domestic violence after Burbank, CA police received a call about an argument between a man and a woman at a local residence.

Sources told us a witness saw James allegedly grab the woman during the argument ... though we were also told officers didn't see any visible injuries at the time.

James, who has been dating Ally for over 2 years, has enlisted legal counsel, who tells TMZ that they "are in the process of conducting our own investigation into the allegations."