I have a Serious Question for You Teenagers Out there!?

My Husband and I just took custody of 2 of our granddaughters 3 weeks ago whom we love very much because their mother (who is my daughter-age 33, has alcohol and drug problem and lays out of work all the time) and a father who works hard but can't manage money and is estranged from my daughter and can't take care of the children also was jailed for beating up our daughter's boyfriend while they were all drunk right in front of the children and when angry and sometimes drunk or high beats our daughter in front of the children. We drove 14 hours from Indiana to Virginia and picked up the girls day after Thanksgiving because of the fear of them being hurt or left alone. They are 9 and 12 yrs. old. We got temporary custody papers good until 11/30/09. Daughter is facing jail time for up to 1-2 years for 3 DUI offense and father is facing time also for malicious wounding after getting 3rd anger management cl from judge in same city. Now that I've given You some background, our problem is the behavior of the 12 yr. old. We have tried to be as understanding and as loving as we possibly could under the cirstances. We know the girls have had a traumatic life. Kourtnee the 9 yr. old is so easy going nothing seems to effect her. She's adapted well. Khailee has said she loves the school here so much better and her grades have gotten so much better as she was failing 3 core subjects but she writes letters to her Mom and leaves them at our computer saying she is tired of our rules and she is tired of dealing with her Grandma and Grandpa and can't wait to get home to her Mom. Our rules are just to protect her not to hurt her. She is now living in a new Town, a new area she is not familiar with, around people she doesn't know. Are we wrong to want to protect her? Please help us with this. Any insight You can give us would be very much appreciated. Thank You in advance and God Bless You. It's been a long time since we've had small children living with us. My youngest is her Mom.