Mom won't mask for her immunocompromised spouse

I am the most covid cautious of my family by far, but my dad and sister both mask indoors and avoid indoor dining for the most part. My mom refuses to mask, even in very high risk places like airports. In fact she flew while actively sick without a mask and then tested positive for covid just a few months ago. My dad has several immunocompromising conditions, but they're very well managed, so functionally his immune system is only a little below the standard. But when my mom gets covid and gives it to him, she recovers in only a few days and he remains sick for MONTHS even after paxlovid. This last time (his second infection, her third) he got a secondary infection, thankfully not pneumonia, that lasted nearly two months.

It's so frustrating!!!! People like my mom are the reason I feel I have to be so serious about my precautions! She's out here knowingly spreading covid and downplaying the effects even while seeing her partner of >30 years becoming ill for months at a time on top of the many serious conditions he's already dealing with! It's just such blatant cruelty and lack of care and it hurts my heart.