I would use her throwing out the notification as an excuse for not showing up in court, and consider suing her (perhaps pro se in small claims court),
Answers are for informational purposes, not legal advice for your specific situation. www.appealsandhabeas.com
In order to sue your room mate, you would have to prove that she threw out your mail (either intentionally or negligently), that she owed you a duty to keep the mail (such as knowing you were going to return for it), that her throwing out the mail caused you to get the warrant (which means you will have to prove you had no idea that the traffic violation occurred at all and was not coming to you at some point), and that the throwing your mail out caused physical, emotional, financial damages of some kind.
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