According to the Clark County District Attorney's Office ... prosecutors are dropping the 2 criminal counts they'd filed against her this summer -- assault with a deadly weapon constituting domestic violence (a felony) and misdemeanor battery constituting domestic violence.

Unclear why they're letting it go -- we're trying to get clarity from the D.A. -- but in any case, Jenn is walking free from this one.

You'll recall, Harley -- who shares a daughter with "Jersey Shore" star Ronnie Ortiz-Magro -- was arrested and subsequently charged after her now ex-BF, Joseph Ambrosole, claimed she pointed a gun at him and threatened to pull the trigger during a nasty altercation while out on the town.

He also alleged she dropped the n-word repeatedly while doing so. This, of course, followed what we were told amounted to Jenn driving off with Joseph's car and leaving him behind following an argument they had at an establishment.

All the fighting was supposedly over Jenn's drinking -- something she'd addressed by checking into rehab. Her attorney, Michael Cristalli, had also told us the domestic violence charges against her wouldn't stick because they were "unsubstantiated."