You can either externalize this, or internalize it. I suggest the former rather than the latter, but obviously that is going to take some serious change in your mental attitude to whats happened.
I think you should get angry about it, pour your efforts into securing your property & the names on your bills for the last months of your tenancy (for peace of mind). Speak to your landlady in person and get her to help you out with this, make it clear this is very urgent and important to you. Severe all ties with this woman, like she has done to you.
Do not expect to get reasons or an explanation or even an apology from your ex. What she has done is despicable and cowardly, she will do everything to avoid admitting fault or explaining it because she knows how wrong she is.
It's going to take time to heal, in the meantime, whilst you are still ruminating and wondering how she could do this to you, try instead to think of your action plan, list the things in your head you need to do to get away from this mess. Do not let setbacks get you down, if you cannot change the locks for example, go out to B&Q and buy an extra lock to fit to your property. Start looking at new properties, you need to get out of that flat and anything that reminds you of her, dump her stuff too, she's doesn't deserve it back.
You need to stand up and fight, anyway you can, show this piece of **** you won't take it lying down, your better than her, you deserve better than that.