When i get into shit like this it really irritates me, but do nothing, nothing at all. Get over friendly towards her, if you go on a vacation or out of town always sent a postcard to her. Smile at her everytime you see her, and say she looks good. When you meet friends of her tell them she is the best girl you ever met and she is a miracle to the world. Keep on doing this, dont give up, giving up is for loser stick with the plan. Be friendly and praise her. In the meanwhile time passes and in that time she thinks you are sick fuck for being sickly friendly with her it will make her shit out the positive energy you are sending. But dont fuck her in that time dont get involved again. When 2 or 3 years have passed it is time to strike. Never and i mean never take revenge immediately in cases like this. She must never know the revenge came from you. Maybe suspect but not more than that.
Since you have had a relationship with her you know a lot of her, use it to your advantage and be reckless. If you arent smart enough to come up shit with what you know of her we have to go, straight blunt in general. Go to a slaughterhouse and get a bucket of blood, say you are studying biology and your professor asked you to get it for an experiment, those guys will give it to you, take a bucket with you. Also ask for disposal meat and guts. And try to get some animal heads too while you are at it.
Now the following needs to be done, find out what day she isnt at home. Or if she is as home be sure she sleeps and no one will notice you. Go to her place and in case of a garden take a shovel with you. Bury the animal heads in her garden at different places and try to bury it real nice.
When that is finished take out your animal blood and a brush or something, and paint the windows with blood and the front door. Also paint some words on her place with profanity and threats. Like "I will kill you bitch!", i am sure you will be creative enough to come up with some sick shit to write down.
Next step put some guts through her postal thingy and scatter guts around in the front of her door.
These things should be done at night, and dont get anyone to stay on watch out, they will betray you later on or when they get drunk. Plan it carefully and dont get caught. Kinda hard to explain.
The finishing step, you still got a lot of disposal meat at your hands, leave it a couple of days to rot and get some starting maggots up in there. Put that heap of misery in a good box, like real good so no one will smel what is in it. Isolate that shit. Go out of town for a day and send that box to her adress. DONT PUT YOUR OWN ADRESS ON THAT BOX or YOUR NAME. She will freak out when she gets that box. Repeat the box thing for the next couple of years and when she gets a new friend also sent one to his place heheheh.
When you hear about this from her or from friends, act shocked. Say she should stay a couple of days with you and say there might be a lunatic out there trying to kill her., hehe. Offer to stay a couple of times at her place. Warn her she should get new locks, and a gun or something and say she shouldt go out alone late...
Goodluck hope you will use this one.