The first thing you must ensure is that your daughter goes to bed peacefully. Her bedtime routine should be calm and very comforting. You could lie down next to her for some time and read out a story to her or even sing her a nice soft song, which would help her relax.
Make sure you know what transpired during her day so you can talk about anything that upset her- this will help lay that matter to rest in the child’s mind. Also, make sure your child does not witness any arguments that anyone in the family may have or for that matter anything that could upset her. Your daughter seems like a very sensitive girl and such children need to be dealt with very carefully.
Assure her of your being close to her and try not to expose her to anything that may be violent. Speak to her casually so that she tells you of her worst fears and gets it out of her subconscious.