Every child is different but i raised 2 teenage girls. Since early on i raised my kids with a choice. Kids can reason as early as 2. Tell them the rules, if you do this then this will happen,,, and follow through with the punishment!!! Dont give in or let them off the hook. You have raised them with your morals and values now its time for them to try to use them wisely. Telling them straight out NO always means " Im gunna do it anyway". But give them a choice and they tend to think twice. Remember this is the time they break the apron strings. Im glad not only was I their Mom but their friend. They are 29 n 28 now and still come to me 1st before i find out elsewhere lol i trained them good.
I used to agrue with my kids and realized they were winning! I stopped arguing and said just do as i say end of story im not listening anymore you knew what would happen,,, its happened now you deal with your choice.Then they stopped fighting it was peaceful again. Just keep the upper hand dont let them get it or u lose in the end and they go wild.
I ruled what my kids wore. Example.......when they were growing up baggy pants were the rage. I said you can have them as baggy as u like BUT if i can pull them off you, you cant have them. No butt crack allowed. No shirts above the belly button. no skirts that if you sit i can see your undies. LOL My kids hated me then but love me now for it. When they said "I hate you Mom" i replied easily with "Then im doing my job right"
I wish you the best. Just remember what all you have taught her. She may look 18 but she wont be able to act it, yet. You cant change how others see her just how she handles it firsthand.