Bethenny Frankel thinks she got motherf***ed by a notary public -- or more accurately ... mother-in-law f'd.
The 'RHONY' star is suing attorney Jamie Andrew Schreck for allowing Jason Hoppy's mother to notarize a trust they created for a swanky apartment back in 2011 ... happier times for the then-couple.
Sources close to Bethenny claim Schreck should've known Carol wasn't authorized to notarize docs in New York state -- and Bethenny thinks this could render the whole trust invalid.
According to the docs, she's suing for legal malpractice, breach of contract, fraud, notary misconduct and breach of fiduciary duties. Schreck had no comment on Bethenny's lawsuit.