Captain Sandy Yawn steered herself straight into a courtroom showdown … accusing a contractor of pocketing millions of dollars from people like her and leaving dream homes half-built.

The “Below Deck” boss showed up in a St. Johns County, Florida courtroom Tuesday and went face-to-face with Spencer Calvert, the ex-Pineapple Corp. owner, in a victim impact statement … telling him point-blank he had wrecked her financially.

Sandy didn’t hold back … she said while he was still chilling in his big home, others like her were left scrambling to pick up the pieces.

Calvert had taken a plea deal … but that deal was rejected this week following objections from alleged victims in court.

Calvert is charged with organized scheme to defraud, misapplication of construction funds, and grand theft … all felonies — WTLV-TV reports 13 victims suffered an estimated combined loss of $18 million. 

Yawn pushed the judge to lock him up for at least 10 years … blasting the plea deal that would’ve meant 5 years behind bars, $1.47 million in payback … and what Yawn basically called a slap on the wrist.