My gf left me and she took my dog which is registered to me...?:
If you purchased the dog in Florida, and you have resided here together and or apart for over a year, then the Courts in Florida would have jurisdiction over this case.  You can retain an attorney to file your claim here in Florida and have her served with papers out in Cali.  If the dog is registered in your name, I don't fore see a problem with you getting the dog back.

Good Luck and Take Care