An interesting conundrum indeed. Though she has the right to free speech, since the state technically owns the plate they can recall it and likely for any or no reason at all, completely legally, so long as they honor the commitment she made to them when she purchased the plates by issuing her credit for the unused portion of her registration.

Personally I think recalling the plate because of a single complaintant (who never has to be announced, leaving the possibility open that there never actually WAS a complaintant at all!) is waaaay too PC for my tastes. Since this is not a sexually or a moralistically based statement she's making, I don't see how anyone could violate her 1st amendment rights by denying her right to make such a statement.

Again however, the rub comes in that the plate is "technically" owned by the state and not her, so in allowing this statement to be made by her with their property essentially would show support by the state of her comment, which it doesn't care to do from the sound of things.

.