Erika,
It must be really frustrating to see that despite all your efforts, nothing is being done about this person who is
driving without having a full driving licence. People like this should not be driving because they are a danger to other people. The problem with the police is that they rely on evidence and if they didn't catch the lady driving on her own red handed, it is difficult to prove that she was indeed driving without a proper licence. This also goes to the family members who are teaching her without having a licence for at least 3 years.
The only thing you can do is take a picture of her when she is driving by herself or film her instead. You could use that as evidence and the police will therefore need to look into the matter more seriously.