Failure to transfer title is NOT a Felony. However, you want to keep your record clear and I highly recommend you retain a criminal defense attorney licensed to practice in the State of Washington and pursue your rights in court. Good Luck!
If you qualify for a public defender, one should be appointed. Don't plead guilty until you speak with an attorney. Bring your proof of transfer. You may be able to have the charge reduced to an infraction.
When you go to your arraignment, you should fill out the questionnaire to see if you qualify for a public defender. He or she can help you decide what the best options are. If this is your first criminal charge the prosecutor may be willing to amend it to an infraction if you provide proof that you transferred the title after the incident, but you should talk to an attorney before entering into any kind of deal.
This answer is for educational purposes and is not intended as legal advice.