Oo dear redhead, if she slept on the sofa knowing you were in bed with the bloke she was sleeping with (I take it it was casual? not boyf/girlf thing?) why didn't she do something then? Why threaten now when you've gone, I think she's all talk and is just trying to keep you away by threatening violence.
This Danny should have a word with her, esp if their not actually going out together but I am guessing he is probably liking the fact that this is happening over him!
Could be a good idea to lay low for a while but if she or anyone threatens you or you feel in danger then go straight to the police please!! Let this Danny know that you will not be threatened and will go to the police, maybe he will pass it on!
Keep safe! xx