What is the best way to handle an 18 year old rebellious child?

My daughter is an 18 year old high school senior. She has a car and drives to school.(My mother gave her one of her old cars) Her school dismisses at 3:30. One day she hadn't made it home and it was terrible weather and was 5:30 in the evening. I texted her and told her that I knew she wasn't still at school and I expected her home immediately. She came home about 10 minutes later. When she arrived I wanted to know how in the world she was so late getting home. She said a couple of her friends cells were taken by administration so she took them downtown to get them back. I immediately told her that it's not HER responsibility to get a child's phone back but THEIR parents. I furthermore told her that she should of phoned and ASKED if it was ok before going. Also that it's not a good idea for her to be hauling these kids all over town and their parents not knowing. What if there's an accident or she takes them in a store and they steal something. They will all be jailed and she will get in just as much trouble because she took them there. I then told her if she can't obey I will take the car back to my Mom and she won't get it back till after graduation. Ok ,she must of gotten furious because 2 days ago my 10 year old twin daughters found a notebook with many pages of things that she wrote down. Basically she said she no longer has a family and her whole family is evil. She said that she wished she was dead and that everyone on the earth was gone except my Mother and her boyfriend. Some of you may have read my question with things about how my mother raised me and they type of person she is. She also said that she sometimes thinks about getting her things and leaving home too. There were a lot of hateful names that she called me and hurtful things she said about me. I have always been a good parent to her. I have always been home with her and tried to raise her right. I had a terrible childhood and a horrible Mom. That's why I try to be the best at raising my children. I know my Mom has put a lot of things in my daughter's head that's why she's praising my Mom so much. My Mother told me that my daughter swears all the time around her. Then told me not to tell my daughter that she told me. I'm thinking she allows her to swear around her it wouldn't surprise me. I know she just sits and laugh instead of getting on her about it. If not ,why does she cares if my daughter knows that she said it? I'm just so fed up with this rebellious attitude. I'm thinking that I should get her counseling and tell my Mom to go away and stop influencing my child. I know my daughter will fight me on telling my Mom to stay away. What would you guys do in this situation?Thanks....