She basically only needs value of house/equity and other possible assets. UNC has a simplified form.
Not suggesting she forge the signature, but if the mother doesn’t have to fill anything out and just had to sign at the bottom, it’d make things easier. The issue isn’t total refusal - the mother has given a number and information, but op doesn’t think it’s true and fears a fafsa verification. So, the snooping would be to verify the mother didn’t give a random number, and checking tax returns is a good way to do it.
An issue here is that mother is growing resistant to OP going to college.
When parents refuse for their kids to be educated (either because they fear they’ll get brainwashed or because they fear they’ll get too big for their breaches and will look down on them) the kid shouldn’t meekly obey and stay home. Sorry, it’s not the 19th century, even in North Carolina.
Op has been admitted to his/her state flagship, which meets need. S/he needs some basic information and needs to verify that the numbers provided by the mom are accurate in order to comply with the flagship’s request.