“If I go to rehab, you’re going, too!” In a brutal showdown, longtime substance abuser WHITNEY HOUSTON threatened to send troubled teenage daughter BOBBI KRISTINA to rehab.

But Krissi (as she is called by friends), 18 – who was photographed snort­ing cocaine earlier this year – shrieked back that she wasn’t going alone!

Now BOTH women have checked into separate rehab facilities in Malibu, Calif., to get treatment for their addictions.

“You’re ruining the family name!” Whit­ney screeched during the recent blowout. “Whether you like it or not – you’re going to rehab!”

But Krissi, who knows all about her mother’s struggles with booze and drugs, yelled back angrily: “What about you? You’re the one who’s destroying us! You’re the one who’s a mess!

“If you can do drugs and booze, so can I! Now you’re demanding I go to rehab. If I go, you’re going, too!”

In March, The ENQUIRER published exclusive photos of Bobbi Kristina, then 17, snorting cocaine.

 In our May 16 issue, we reported that the drunken teen had been involved in a 4 a.m. gun brawl on April 1 in Georgia that resulted in her being charged with possession of alcohol as a minor.

She is scheduled to appear back in court on May 24 and faces six months in jail.

Meanwhile, Whitney is still battling her old demons, says a family insider.

“I think Krissi has a serious drug problem, while Whitney has a problem with both drugs and booze,” said a family insider. “Whitney will mix drugs and margaritas.”

According to the source, mother and daughter are outpatients at rehab centers in Malibu that are 15 miles apart.

The facilities allow Whitney and Krissi to go home at night instead of keeping them under con­tinuous supervision.

ALL the details are in theENQUIRER!