Its all good, you can make it up by doing good to others now. Heres some advice from someone just like you. I was always a push over and overly kind to people. I guess being overly kind was a way of me being afraid to be not liked. The reason all this anger built up inside of you was because you did not stand up for yourself from the get go, allowing her to feel brave until you just couldnt handle it and snapped. She said pay for groceries. Uhm no that wasnt apart of the deal i dont even eat bread. Pay for electricity, uhmmm no your the landlord. Take my guitar, uhm thats theft give me my shit back before i call the cops. Because yu let her or anyone else push you around these feelings build up. Until you cant take it anymore. Inagine of you delete everything from ur story accept she stole from you, this would not have been your reaction it was a culminating event which you let grow. I let a coworker do it to me.for 1 year and eventually slapped him across his face and got fired. If i didnt put up with that from day 1, that wouldnt have happen. Glad to see this was a long time ago i guess i missed that part.