Help! Our grandaughter may have been lured to some sort of hard drug?

Our grandaughter is 15 and we have both been with her since she was born. I'm grandpa and I've never been so close to anyone and my wife ever. She was herself until march of this year as they were living with us since our daughter got evicted. Our daughter got divorced a year ago and she has not once paid her rent. She also has a boyfriend that is a known drug seller. They moved 50 miles off. Incidentally our daughter has disowned us and we've never done anything to her. Her personality also changed drastically. Our grandaughter recently started having an aggressive attitude with us and she was very mean to me on Facebook. What do we do? Our daughter also lost custody of her youngest, two months ago. The children services and the court pretty much told us that we have no rights. We are about to go crazy worrying.