Careful

You should file a police report immediately. Have the police come to the apartment and talk to her, which they will if you tell them she loaded a gun and put it under the pillow. Police may question why you didn't call them last night, but you could say you were in shock or something. Police always come when guns are involved. Make sure your paperwork is in order on them.

This will show her you mean business and you can't be fucked with. The law will have a record on her and if the cop is a good one, he'll give her a very strong rebuke and lesson about firearms and where you end up if you threaten someone with one or discharge it. This could scare her into some sensibility for awhile, or until she begins to think she can kill you and herself and jail then won't even be a possibility. Regardless, having 2 or more police officers in your home poking around can have a chilling effect on future violent action for some time.

Clearly, the emotional, irrational elements of her constitution have taken over. Understand that she is a 30 year old childless woman. Hormonally and instinctually she fears losing her male protector as well as a chance at reproducing near the tail end of her most fertile period. Basically her life is collapsing all about her. It may mean nothing for her to kill herself. Death may be preferrable to the lonely, childless, insecure, impoverished alternative. This may be an exciting thing to be a witness to--I, myself, have always been a keen admirer of the suicidal event and how it precipitates. Only you know the chances on whether she would want to take you with her or not.

Now she knows where your new apartment is, which will be helpful when she starts to stalk you. Very good you told her that. I am looking forward to the phone call where you detail how she attacked some girl you were bringing home. Ah, I am imagining the ugly, ugly scenes now.

I see this ending in a restraining order, an ugly divorce if she lawyers up, with violence interspersed along the way. That you live in the same city is going to make this a lasting, terrific bit of fun for everyone involved.

Good luck.