Hello Carrie,
When I see people who have died in my dreams, I interpret it as a message. I analyze the relationships and associations that I have had with this person .In your case, your friend got into an accident because ".... She was driving down the wrong side of the highway." On the basis of this it seems to me that her message to you is that the decision that you have made recently or some Projects you wanted to start just before she came to you in a dream,is not the right for you that is "wrong side of the highway ", wrong directions.