Bobbi Kristina Off the Hook in Underage Gambling Case

Bobbi Kristina won't be prosecuted for gambling underage at a Vegas casino last month -- TMZ has learned the cops have closed the case due to insufficient evidence.

TMZ posted the video -- showing what appears to be 19-year-old Bobbi Kristina gambling at a slot machine with her 22-year-old boyfriend, Nick Gordon, at the MGM Resort and Casino. The legal gambling age in Vegas is 21.

As we reported, the incident was investigated by the enforcement division of the Nevada Gambling Control Board, but Deputy Chief David Salas tells us, "We have completed our investigation and there is not enough evidence to support criminal charges."

Salas adds, "We are going to close the case."