The bar has now been set for the WORST MOTHER-IN-LAW in the world.



On Thursday, 70-year-old Diana Reaves Costarakis of Middleburg, Florida went to a Home Depot to meet with a HITMAN . . . who she wanted to hire to kill her DAUGHTER-IN-LAW.  And she was willing to pay $5,000 to make it happen.



Fortunately, as in all these cases, the hitman was actually an undercover cop, from the Jacksonville Sheriff's Department.  We're not sure how she found the hitman in the first place, or exactly why she wanted to kill her son's wife.



When he asked her if she was SURE she wanted her daughter-in-law killed, she said, quote, "If you don't, I will."  That's when she was arrested for two felony charges:  Criminal solicitation and criminal conspiracy.



Angela Costarakis is her daughter-in-law . . . and is SHOCKED she was the target. 



Quote, "Three weeks ago, she gave me a big old hug and said I'm so glad we're great friends.  I guess if I was out of the way she could have her son and her granddaughter [to herself]."



(First Coast News)