I think the the inbox/outbox system would work well for you.
Set up a table outside your office or near the door to your office with two little trays, and implement the system. If she tries to bypass, by talking to you about what she's brought you, listen to her, but do not let her put it on your desk. The inbox/outbox system can easily be ignored. Gotta take a broken windows policy on it or it will never work.
I don't know how your office is configured, but if she's pulling reception duty, then you gotta stop that ****. Cut some dead weight somewhere, hire someone young to answer the phone and run errands for the hippie for cheap, and get her moved to the back of the office.