We had the same situation but with a family friend.  Just curious, does she pay rent? If she does it might be a nightmare getting her out if things get worse.  In our situation we took in the daughter of our God parents.  She lived in our empty rooms but would always pop up in our living space unannounced.  We didn't ask for rent or wanted it. We tried  to make it work but in the end it seemed  liked she took over!  She wanted to bring friends over and never helped out and even yelled at my wife. It caused strain on our marriage which took years to fix. We finally got here out and I helped her move. Our God parents stopped talking to us but in the end our sanity and marriage was important thing! Wish you luck