How do I evict a live in girlfriend in who has just had me arrested on a domestic violence charge (which I didn't commit)?

If your girlfriend is not a legal occupant of the premises (ie on the deed or lease), then you can evivt her.  If she paid your rent or utilities she will be considered to be your tenant.  If not she will be considered to be a "licensee"; that is someone who entered and remained on the premises with permission. 

In either event, now that such permission has been revoked the lawful way to remove her from the premises is to serve her with a notice to quit (typically 30 days).  If she fails to leave at the end of that time you will have to go through the requisite procedures for eviction in your state.  Once the court enters an order for her to vacate the property it will be enforced by the sheriff, using physical force if necessary.

What you need to do now is to speak with an attorney in your area.  They will advise you on the correct procedures for all of this.  If you fail to comply with these procedures you could find yourself on the receiving end of a lawsuit for unlawful eviction.  And it sounds as if your girlfriend would not hesitate to bring such an action.

Additionally, is she has gotten a protective order, you can't be  on the premises until she is out.  Again, speak to an attorney as to all of this.