Robert Schimmel's widow is mishandling money from the late comedian's estate ... according to Schimmel's daughter who's accusing her of cheating the children out of their inheritance.
Schimmel -- who had 5 kids -- was in the middle of a divorce from his 2nd wife, Melissa, when he was killed in a car accident in 2010.
His daughter Jessica Katz fired off a letter to Melissa's attorney ... accusing Melissa of failing to pay his children money owed to them. The letter's not long on details, but she claims at least 2 of the kids are owed $25,000 each.
Jessica wants Melissa to no longer have control of the estate purse strings.
The attorney for Schimmel's estate tells TMZ ... Bob racked up huge medical bills before he died, and those creditors have to be paid off first before the heirs can collect any money.