Car Ticket Without Knowledge & Bailing / Court.?

Just received a note from the courthouse on a ticket given to me that did not know about it. I guess ticket was issued sometime last january. Im being told to pay a bail & after that a day will be igned to me to show up in court. Ticket was about expired registration. main problem is car is registered to my fiancee & obviosly she's the one being asked to show up. However, Im the one who drives that car. The total amount for the bailing is 165 dollars. Fiancee obviously does not know about all this...What can I do??? Will she / I have legal issues about all this? She's pregnant, so Imagine how guilty Im feeling about all this, even though I did not know about suck ticket. What should I do?