Whitney Houston's 19-year-old daughter got away with a crime that everybody gets away with in Vegas ... she gambled underage ... and it was all caught on tape.
Bobbi Kristina was facing off with a slot machine at the MGM Resort and Casino Saturday night ... while hanging out with her 22-year-old boyfriend Nick Gordon.
It's unclear if Bobbi actually won any money ... but it's highly unlikely she walked away with anything significant ... because casinos usually require an I.D. before handing over large prizes ... and ya gotta be 21 to gamble in Vegas.
In fact, people under the age of 21 are usually forbidden from hanging out ANYWHERE in the casino area ... so it's a bit surprising BK was able to pull up a chair and hang out with the one-armed bandit for as long as she did.
Bobbi Kristina was in town to attend the Billboard Music Awards on Sunday ... where she accepted the Millennium Award on her mother's behalf.
A rep for the Houston fam who had no comment.
A rep for the MGM Grand tells TMZ, the casino is currently looking into the incident.