Healthy communication when two friends with abuse trauma trigger each other

Hi, I'm new and would love some insight into how to handle communication with my friend who is also my lodger (so complicated by a power relationship). Our relationship is normally caring and reciprocal but I walk on eggshells because I never know whether something I do or say will trigger her. She and I have both had trauma from emotional abuse in our pasts. I have a hard time setting boundaries with her because I am aware of her vulnerability. But my own health is suffering. With ME/CFS and sensory issues, and not being able to deal with aggression, I can't tolerate being shouted at. It's also hard to bring up any practical issues about the household without her criticising me or becoming hyper-defensive and accusing me of criticising her. Once she mis-interpreted something my husband said (he was laughing at our puppy's failed attempts to make friends with her cat, she accused him of saying it was OK for dogs to chase cats when cats were terrified). She went into a weird, dreamy trance like state and accused us of thinking it was OK for her cats to be terrified. Another time she shouted at me for a whole hour, and I felt frozen to the spot, unable to walk away. This triggered an ME flare-up with experiences of depersonalization, which lasted a month. I'm in therapy looking at my own trauma and boundary issues, but still struggling to feel relaxed and safe. The other day I mentioned really calmly and without criticism that I'd like to have a safety rule that we don't put sharp knives loose into the sink to soak, since several people share a kitchen. She immediately shot back that I had done it myself (I hadn't), then she went on about her experience of working in a professional kitchen. Even though this was a trivial thing, it really upset me that I can't bring up even small things without being accused, then her defending herself. I managed to stay calm, and she eventually said 'point taken' but was clearly angry with me. If it's something she already does or agrees with, she expresses that she is offended that I think I need to tell her. I am extremely tactful, something that other friends, employers, etc. have singled out as one of my strengths. I know it's not personal, it is her being triggered, but I find myself avoiding her and hiding in my room rather than using communal areas of the house. Right now I feel burned out, like the whole relationship is at risk, which would also cause a rift in our shared household. Since starting therapy and still recovering from the ME flare-up, I have been more distant in our relationship. She has been really nice to me, but I just don't feel emotionally safe being close with her right now. I feel like I need to talk about it with her but I am feeling very fearful, and also don't have much physical or emotional energy. Advice about how to have healthy communication and boundaries with people close to us who also have trauma would be gratefully received.

Dear KayDeeee,

That sounds so very stressful and distressing. I am so sorry you are in such an unwelcome and unhappy situation!

Sincerely Yours, Yao Wen