Depression Support Group
Depression is a real and debilitating condition that is often misunderstood by family and friends. Its meaning can range from a prolonged period of sadness to an actual mental illness with specific symptoms. Find and share experiences with others who are going through the same struggles.

You CAN control what you do or don't do. Do some research on self esteem. Learn about it, how important is, and how to have it.
Good luck to you. You deserve the happiness you seek.
My advice to you, like I did: Let it go. Forget about it/her. She's not worth your time of day. It's in the past. Move forward and forget about the bitch. I think you'll do much better in life, you sound like a good soul.
But just work on yourself. You are a beautiful, unique person. There is no one else in the entire world just like you! You have a lot of negative self talk that yo need to be aware of and change. Please work with a therapist on this. Mine has been amazingly helpful at combatting my negative self talk!
However it's in the past. We all expect decency from people but there is no law saying it has to happen.
I think some of your issue is the non acceptance of how cruel life can be and an insistence that people who do bad things should suffer. It would be great if they did but you are not God. Life does not work that way.
I'd focus on ways you can move on but if you keep trying to insist the world works differently than it actually does then you are designing a torture chamber for yourself
You can't change their lives. Also, you can't be sure that she has a "happy ending". Does she have a baby? Yes. But depending on how she raises that child, they might never speak to her once they are grown up. She has a husband? Well husbands might cheat or even beat her. Lots of people try to make people think that they have a great life. Maybe she does? Maybe she doesn't. I don't know. All I know is that you can make your own happy ending darling. What do you want to do with the rest of your life? What are your goals? To get married? To have a significant other? To have a baby? Right down your goals.
I know this is like putting a bandage on a knife wound. But I have faith in you.