I think adults really underestimate how hard Covid restrictions are on kids. Sounds to me like your daughter is lashing out at you because she has no other outlets and is depressed and frustrated. Being a teenager is hard enough at the best of times, let alone being stuck at home with mom all day every day (no offence). I remember during the horrible teenage years my siblings and I said some shocking things to my mother, but when one was having a major meltdown the others would pull them back into line before it went too far. Being a single parent is extra challenging in this sense but it sounds like you’ve done a great job so far and will continue to do so. This is a bump in the road and you’ll get through it. Your daughter would definitely benefit from some counselling and some other outlets for her frustration.