Once again, until this friend is 18 they have few legal options and cannot really press a claim to much of anything that their parents do not agree to.
Having ownership means nothing if you can't assert that ownership. Once they turn 18, they are free to go to their state's department of motor vehicles and see what must be done to transfer the vehicle into their name alone, and check with the bank. If they leave home without parental approval and the parents hold onto the car and the bank account, your friend will have to go to court to wrest control from them. He or she might win, but they'd have to go the long way through court. It would be better to simply work with their parents for a way to move out that would appease them.
Depending on the type of bank account, it may be under the control of the parents entirely. Or, it may be something that one or both may agree upon to transfer into their name. If your friend can access the funds on their own, then they can open their own account at age 18 and withdraw money from the shared account into their own. Until then, this may not be possible. Same with the car. Depending on how the title or registration is set up (and I am unfamiliar with these procedures in NC), it may require that both parties agree to a transfer.
Now, a few questions ... and, concerns.
First, you say this person has restricted access to the internet. Yet, they apparently have sufficient time and access to contact you. If they have a phone, a laptop, or most any wifi device, they can certainly do some quick internet searches on their own. It is simply unrealistic to think that they have time to chat with you but not make a couple of internet searches of their own.
Second, have they asked you for money or other resources?
Third, have you ever met them in real life? (As in, in person and face to face without a computer screen, phone or tablet between you?)
My personal thought here is that you are being played. If not for money or financial gain, than for some twisted sense of pleasure on their end. I'm going to guess that the person on the other end of the line is interested in some form of romantic/sexual relationship and has titillated you with that particular lure. The situation you describe, and the circumstances surrounding this "relationship", are nearly identical to many I have read about and even had to investigate because they advanced into the criminal sphere from the ass-hat realm.
Now, I may be completely wrong with my suppositions above, but, this situation has a bit of an aroma to it. But, if I am wrong, this friend still has some choices to make - the top two most likely being ... Move out at 18 and risk not having a car or access to a bank account, or, work with their parents so they might move with more than the clothes on their back or a bitter fight out the door.