Michelle Janavs was just sentenced to 5 months in prison for paying $100,000 to the scheme's mastermind, Rick Singer, to help her 2 daughters cheat on college entrance exams ... and agreeing to pay another $200k for one of her daughter's to be set up to look like a beach volleyball recruit to get admitted to USC.

Before hearing her sentence, the judge made it clear Janavs had caused harm to the U.S. system of higher education ... and prosecutors blasted her, claiming she held an "attitude that she is untouchable" and "no one could stop her." Her lawyers asked for no jail time, but the judge wasn't buying it.

Prosecutors didn't get nearly what they wanted ...  they recommended 21 months, calling her one of the "most culpable parents" charged in the case who refused to accept responsibility for her actions until months after she was busted. Unlike other parents who pled guilty right away, she was also hit with a money-laundering conspiracy charge.

Her defense team went to bat for her, though, arguing for more than 45 minutes that she's a "generous and selfless" person who's "the rock of her family." It also mentioned a time she dressed up as "The Candy Monster" while visiting kids to talk about childhood hunger.

Janavs' lawyers had previously suggested she's just a loving and devoted mother who fell victim to Singer ... and pointed to her history of philanthropy and devotion to her family in urging the judge to not send her to prison.

In the end, however ... it didn't work.

The Hot Pockets heiress now joins several other parents to receive time behind bars in the scandal, including Felicity Huffman ... who got 14 days in her deal. Others have received sentences ranging from probation to 9 months behind bars.