If I could go back and communicate with my teenage self, I would tell her to start that writing project she has always had hidden in the back of her mind. Especially since what she would want to do in college would end up not being all that it is cracked up to be.

As a matter of fact, I would probably tell her to focus on making money and being as financially independent as possible, before even considering furthering her education.
*I truly felt pressured and pushed into going to college right out of high school. Even though I did learn a lot, I wish I did not have such a feeling of regret when it comes to the educational decisions I made.*

One of the harder pills to swallow for her would be my advice to try to make her relationship with a family member work. I understand the pain she went through but the pain of regret now that they are gone, cuts like a wire sometimes. At the same time, I would hope she would give herself grace with how she has been feeling and acting due to those negative feelings.
*The teenage years were some of the hardest in my life, so I would want to give myself as much comfort and peace as possible ultimately*