Michelle Parker‘s ex-fiancé allegedly offered her thousands of dollars for sex just one week before she mysteriously vanished in 2011 … TMZ has learned.

According to newly unsealed court documents, obtained by TMZ, investigators point to a text exchange from November 10, 2011, between Michelle and Dale Smith Jr., who is now charged with her murder.

Per the docs, Michelle rejected Dale’s proposition, texting him, “Thought about your offer … & will have to decline. I’d rather have a personal legal loan than feel like a whore.”

Dale allegedly responded that he wasn’t trying to make her feel that way, insisting he simply wanted to spend time with her.

The arrest affidavit shows Michelle pushed back during the exchange, accusing Dale of offering $2K in exchange for sex. It appears Dale acknowledged wanting to spend time with her but denied that his offer was a sexual transaction.

According to the authorities, the disturbing exchange came just one week before Michelle, a 33-year-old mother of three, disappeared on November 17, 2011 … the same day an episode of “The People’s Court” aired featuring the former couple battling over a $5K engagement ring.

Michelle was last seen dropping off the twins she shared with Dale at his Orlando home. Her abandoned Hummer was discovered the following day, but her body has never been found.

Investigators now believe Dale killed Michelle inside his home after she dropped off their children, following weeks of bitter arguments over custody and their relationship … with authorities saying Dale had scratch marks and abrasions believed to be defensive wounds.

As we reported … Dale was arrested October 14, nearly 15 years after Michelle disappeared, and charged with second-degree murder after advances in digital forensics helped investigators reexamine old cellphone evidence.