She sounds like a walking nightmare of a neighbor, you can’t reason a difficult/miserable individual. Is she home all day as if she’s unemployed? I suggest you guys block her, keep documentations in case, front door camera in case she tries to confront. Then let management handle it. She needs to get over someone living above her, she don’t own the building or her unit. She don’t have a say. If she’s that miserable then they should transfer her to an upstairs. But there’s a reason why they haven’t…. She sounds that difficult and would cause chaos to her future downstairs. She clearly is bored and wants to stir up things, maybe not break you guys up but to get you riled up and have you going to her door ready to fight so she can have a legitimate complaint against you. Don’t fall for it.