Sparked Rehab Decision

Luann de Lesseps going back into rehab might have shocked fans, but the people closest to her knew she was only pretending to be sober for weeks now … TMZ has learned.

Sources close to the ‘Real Housewives’ star tell us she fell off the wagon at least 2 weeks before Bethenny Frankel announced her ‘RHONY’ pal was reentering a rehab facility — the second time in less than year.

We’re told friends point to a July 2 pic…