I'm so sorry you are going through this. I feel for you since I have a dog that acted the same way as your Bella does. I had so much support from YTers and they helped me turn him around. He's such a good dog now.
He wasn't covered in ticks, but he had so many fleas that his entire snout was so covered in flea poop you could barely see the skin. If you ever need anything, or just to have someone to chat with that's been there, feel free to PM me. Bella can be a sweet and loving girl for you with time.
Please don't breed her. I received advice from a reputable breeder that her fearful personality can be passed on to puppies. One scared dog is enough. Please spay her and love her for the rest of her life.
Again, my heart goes out to you since I struggled with a similar situation. But know there can be a bright and happy outcome in the end.