What happens after my girlfriend went to register for probation and got arrested for a warrant for unlawful use of a credit card?

A skilled criminal defense attorney would need to discuss this matter in greater detail with your girlfriend & you, & ask her many questions, in order to give you folks the complete, proper legal advice you need (& a quote to represent her).? Schedule a consultation ASAP.? Once the matter is resolved to you folks' satisfaction (hopefully), you'll both be glad you paid the money to hire an experienced attorney in this field who knows the correct actions to take to properly protect her legal rights.