Meg,
I agree with J-9. I don't think you were lashing out but venting. You've kept it inside for so long and It's come to a boil inside you. Letting it out is a good thing. It keeps you from turning it inward to yourself which is dangerous.
You can call your county department of mental health to find out about affordable therapists. They can give you names and help out.
It's okay to be angry. No one is doubting you or thinking you're making more of it then it was. No one can walk in the shoes you have. You're right about the emotional scars they take longer to heal.
You can go through the depression and addiction if you allow yourself. But someone I feel is very strong and by no way immature can choose the path you take.
Getting help and being able to talk it out gives you the chance to learn to heal. Some people are not worthy of forgiveness. Some people don't deserve to live a life full of scars and mental pain. As for friends, you found some here. You don't have to agree with all or any of what we say. We just ask that you hear us out. From there make your own decisions.
Trhu our own experinces and mistakes, we'll try and help you with our insight. As I tell my boys. There's no failure or mistakes if you can learn somehting from them and apply what you've learned. We'll tell you what we've learned and you decide if you can apply it to your life. You're so young and strong, Meg, don't let the past defeat you or deprive you of a happy future.

Chippers