Your sister will need to call the court listed on the ticket to find out exactly what steps she needs to follow in order to take care of her citation for operating a motor vehicle without a license.
NJ Statute 39:3-10 states that no person shall drive a motor vehicle on a public highway in this State unless the person is under supervision while participating in a behind-the-wheel driving course or is in possession of a validated permit, or a provisional or basic driver's license issued to him in accordance with this article.
A person violating this section shall be subject to a fine not exceeding $500 or imprisonment in the county jail for not more than 60 days, but if that person has never been licensed to drive in this State or any other jurisdiction, he shall be subject to a fine of not less than $200 and, in addition, the court shall issue an order to the motor vehicle commission requiring the MVC to refuse to issue a license to operate a motor vehicle to the person for a period of not less than 180 days.
Since jail time is one possible penalty for being cited as an unlicensed driver in NJ it is likely that your sister will need to attend court, but she can find out for certain by calling the court.
Your sister can find out more about penalties for driving without a license or even better, how to obtain a valid driver's license by contacting the NJ Motor Vehicle Commission.