I got shivers reading your first post, carole, as you pretty much summed up the relationship between myself, the fifteen-year-old, and my mother. We don't always get on.

I would say that from your daughter's point of view, she probably doesn't appreciate being told directly (kinda silly, but mood swings I suppose ). I know I'd be more inclined to do something if it was implied I did it. For instance, if I did happen to not want to wear suncream, and my mum said "Zara, put this suncream on now!", my gut reaction would be to create an excuse, i.e. "But it'll stop me getting a tan!" or something of that nature. Argument follows.

I know I'd be far more likely to do that if, instead of demanding me to put it on, my mum said something along the lines of "You look really nice today, Zara. The suncream's just on the table by the door for you to pick up as you go out." That's set me in a good frame of mind and I'm most likely to oblige as it's, more-or-less, my own choice of action.

Of course, not saying this will definitely work, but just thought I'd add my own experiences as a teen. Remember she probably regrets the arguments more than you (I know I do).

ETA: I also wouldn't use the often-heard 'you'll regret it later' scenario with her, yes, you're right in what you're saying, but I know if it were me it would make me feel even more spiteful and less inclined to obey. Just a thought.