Perhaps it's time for a heart to heart talk with Elizabeth, before dumping a long term relationship? You said she's going through a lot a difficulties right now. That's not an excuse for bad behavior, but, stress does cause us to behave in ways we wouldn't normally. She may need a friend she can talk to about these issues, but, more likely, a suggestion to see a good counselor who can help her sort things out objectively.
On the other hand, you say that you are "paranoid" about people, and drug yourself to make it all go away. I'm sure you know that's not a healthy response to your own feelings. Have you considered getting support yourself?
You don't say what type of drugs or how much. Perhaps NA is the answer. Or just choosing a healthier lifestyle. Talking out your feelings with a counselor may be a good starting point for you too. Certainly coming here and talking about things was a start. Continue to talk it out. You'll find your way.
Shalom!