When our attachment relationships (partners, kids, parents, "my person") involve someone who has lived through a trauma nightmare (or 20)...we need to know the difference between safety and FELT safety.
Trauma f's with a survivor's nervous system and makes it harder to feel safety even when safe.
This is where a secure loving attachment figure is key...you can lend your grounded nervous system to this person by being present to their fear and dysregulation with an empathetic and calm stance. Offer patience and compassion and as they ride whatever wave of panic they are surfing by being WITH them and not pressuring them to feel safe, but being a safe person for them to feel unsafe with.
Eventually your relationship will be a space of safety in a world that is trigger happy to your loved one.