CPTSD: How to ask my DM to give me space?

[TealGuide]

As I go through therapy, understand and explore my past traumatic experiences, I find myself unable to pretend everything is normal around DM. We are low contact anyway but yesterday she rang me and it triggered me massively. The phone call was less than a minute, I told her I was busy and I'd call her another time. I do not want to nor do I feel able to talk to her, I just freeze. Since therapy, I Freeze and get angry. It's like I want to Fight but physically can't. It's not good for me.

How do I tell her I need space? I'd like to do it maturely/gently/politely. To be honest she really gets my back up and I never talk about personal things with her so I don't know how to go about this.

She is the reason for a lot of my trauma and I would like to eventually cut her off but I am not ready to do that yet. Thank you.

[TealGuide]

I should have added I don't really tell her anything. She doesn't even know I am going through trauma therapy - that feels like something far too personal but I'm at a stage where I have to address contact levels for my own wellbeing, it's causing me too much anxiety not to. Especially when she wants to maintain contact (albeit rarely).

[Eyesopenwideawake]

Simply don't pick up, let calls go to voicemail and then text back at a time that suits you.