Not wearing mask when around my newborn

I'm so freaking pissed. My newborn is 28 days old. Me, my husband and my mum(who helping me with my confinement) is covid positive so i urged everyone to wear a mask when holding my newborn or whenever they're near her. My mum occasionally wears her mask around my newborn. Sometimes she wear sometimes she don't. Sometimes her mask is not worn properly. She keep playing with my newborn without wearing her mask properly at times. Like if you care for your grandchild you would've do anything to protect them right? Why is she taking things lightly? Like does she not care if my newborn got covid? (Well i suspect she might already contracted it from my mum being very irresponsible) I've not told her off because she is a very sensitive person and is helping me with my confinement and I don't want to make her feel like I'm micromanaging her when it comes to my baby but i know everyone is gonna tell me to just tell her off because at the end of the day I'm the mother. Yes thats true but I feel like I'm being put in a position whereby i don't wanna hurt her feelings its like so paralysing I don't know how to put it into words. I feel like I'm slowly going into depression because of this ontop of other things that has been going on. As I'm writing this, she's feeding my newborn milk without mask and she's still positive. I feel like banging my head against the wall.