You need to first go to the court and let them know that you were the one responsible for getting the subpoena delivered, and you failed to do it. Only YOU have a chance of fixing this...at least as far as giving your boss more time to do what she was supposed to do. Your JOB however, may be on the line now.
Keeping your job isn't worth her going to jail. Although I'm with Jess ^, subpoena's are supposed to go DIRECTLY to the person, not to their receptionist or anyone else. ♥ -
It's not your job to give the subpoena to her. That is the job of the police department. In fact, it's illegal for them not to give it to her directly, as far as I'm aware.
In agree with Jessica, Lauren, Heather, and Missing Chaya Eliana. You HAVE to go to the police first and let them know. THEN tell your boss so you can also say "i'm really really sorry, but i have gone to the police and fixed it for you." Maybe she'll forgive you and you can keep your job. You just never know but you HAVE to do the right thing here.