As everyone else has mentioned, you have to do what's best for yourself first. Some people grow up seeing toxic behavior as "normal" and don't realize there is another way to get their thoughts and feelings across and their needs met. It's very sad that there are humans out there that don't know how to express any positive emotions. When you contribute to that behavior, by allowing her to treat you so poorly, the cycle continues.

We've all had horrible experiences in life, difficult marriages, childhoods, trauma's. One cannot use that as an excuse to continue abusive behavior. If you decide this is the relationship you want to be in, make sure you set some boundaries and stick to them. When you see that she's losing control, leave. Do not return until she's rational again. If/when you do return let her know that you love her, but you cannot live under these conditions. Then it's her choice whether to respect your needs or not.

In the meantime, if it were me, I'd set up a plan B. Get my own place to live, expand your social circle. If she's not willing to seek help for her issues, YOU get help. Find a therapist to help you learn to establish boundaries and a healthy self worth so that you do not tolerate abusive behavior.