First, is there anyone you can leave your dog with for a couple weeks so you don't have to worry about him anymore? Maybe family?
IANAL, but I'd look into recording conversations with her in the future. That way the next time she tries to threaten you, you have a record of her being aggressive and threatening, so she can't make up an act should you defend yourself against her. I'm not sure if Texas law requires you to notify all parties that you're recording, so your mileage there might vary.
I'd also try talking to some people who deal with mental health issues, etc. and see if they can't do anything about it. She sounds like a certified nut case so there may be a possibility of getting her ass in jail based on mental grounds.
The last thing is disparity of force, so this means if you have to use deadly force to defend yourself against her, you damn well better make sure she's wielding nothing shy of a 3 foot sword. Sucks, but I think that's the reality you're looking at with her.