If your girlfriend was in an altercation where law enforcement came to your home and questioned her outside of it, but she was within the home, and based upon what she said there was probable cause to believe that a crime was committed, the police did not need a warrant to arrest her because she was right there.From what you have written, there was nothing indicating a 4th Amendment violation regarding your girlfriend's Consititutional Rights. I suggest she consult with a criminal defense attorney.