My wife is exactly like that. Catastrophizing - jumping straight to the worst possible scenario - because that’s been her history (or at least, her childhood and early adulthood was like that - she grew up in a complex and traumatic environment).
Arguments often arise from this. Less so, recently, as we’ve been working through it together, but the pattern of “perceived crisis - crisis response - different perception from other person - sense that other person is abandoning - which is another crisis - escalation - repeat” is still in the background and flares up sometimes.
Our childhoods carve riverbeds of thought patterns - habits of flow for our thoughts - and if we let our thoughts flow their default pattern, we tend to reproduce the flow of the past, in the present. Crisis, catastrophe, may have been the case in the past, and crisis response may have helped us survive then, but it isn’t working now; we are in a more stable present, and we need to explore new ways of relating to it (and to the people in it). We are no longer surviving. Now, we are thriving (or at least, learning to thrive).
I have found lots of gentle, nonjudgmental listening has helped her. Each day we take 15 minutes and listen to one another. No assessment, no advice, just listening. We use “I-Statements” to help keep focused: “when I see / hear [something concrete and quantifiable, like ‘the garbage not taken out’ or ‘you not wearing your COVID mask indoors at your shop with your colleagues’; not something that’s more general like ‘you disrespecting me’], I feel ____ [a feeling word like ‘I feel like I don’t matter to you if you don’t take time to take out the garbage’ or ‘I feel in danger, like you’re abandoning me, when you don’t wear your mask, or when I feel doubt about whether you’re wearing the mask’]”.
(Edit to add: the I-statements can be about anything; they’re not just about her or me. For example, it could be: “_____ happened at work and I felt ” or “ said ____ to me today and I felt ____”.)
This listening helps her get her feelings and thoughts out of her head. When they’re in the head it’s like they get into hyper-expansion mode and they just scale up and become overwhelming. When they’re out, in words, with shape, they have limits and we can look at them together.
The listening is about hearing, not judging or advising. I will respond by simply echoing her: “it sounds like you feel ____ when you see/hear ____”. It’s just about being heard. After about 7-8 minutes of her sharing, I do my sharing. (We set a 15 minute limit because sometimes the topics are emotionally heavy and if it’s longer than that the exercise starts to feel intimidating. 15 minutes is digestible and helpful.)
Listening time can be with a trusted friend or group. Sobriety meetings like AA are great for this. Meetings can be attended every day (which is a great chance for sharing every day!). Many meetings are open to people sharing things with the group. That sharing, that giving words to our thoughts, is empowering and liberating. There are meetings of all types, including some mixed and women’s only meetings (that can be helpful sometimes): Resources for our recovery
Another thing that’s been helpful is therapy. Therapy! I would recommend it to anyone. All the time and money we used to spend on our addictions, channel that into therapy. 
(if you can’t afford therapy though it’s not a big deal, because a good meeting does more or less the same thing). There’s a great article about a tool called Dialectical Behaviour Therapy, here:
In sobriety and in life post-CPTSD, we are building new pathways for our thoughts and behaviours (our responses to our situation / life, and emotion - the thoughts and behaviours are responses to those). It takes time but it is possible. Just like recovery, take it one day at a time and keep asking for help. You will find what you need.