About the OP’s concern that failing students are full of despair and self loathing – really, it would be hard for the student’s despair and self-loathing not to worsen when the student’s mom thinks she needs to be directly involved with the professor-student discussions about incompletes. Despair ultimately is a feeling of helplessness and the mom’s actions wouldn’t be helping with that.
Faculty often are discouraged from granting incompletes without there being a clear plan of action put in writing for completing the work as many students requesting incompletes never complete the work. Parents can certainly provide input to the student’s correspondence with faculty about the plan for completion.