If your girlfriend wants to transfer her car title over to your name she can. You will have to pay the applicable tax, title, and registration fees. The total cost for the transfer of title will vary depending on the make, model, and year of vehicle it is. You will also have to get the appropriate insurance on the vehicle for yourself and whomever else is going to driving the vehicle. The cost of insurance will vary with the type of vehicle it is your insuring, your past driving history, the number of licensed drivers you have on your insurance, and what you are using the vehicle for.
If you have further questions about transferring a vehicles title, you can contact your local Department of Motor Vehicles for specific information. The representative can answer any question regarding estimated of cost, the information necessary to complete the transfer, and who needs to be present during the transaction.