Am I overreactting ?

So as in my last post I had mentioned that my mom had surgery. So I had most of my family come down for a visit to help out with mom's recovery, but yet only made me stress out even more. 
I know that I am way over my head with trying to help out and un pack and trying to not get sick and make my mom sick too. And I let somethings slide between my fingers because it happens. 

I know that I screw up occasionally , but then also I did just sort of get handed this job of being a care giver and I haven't quite gotten it under my belt just yet. 

This next part I'm still having a hard time to get over that hump of I am ok. My sister had gotten into an argument with me while I was getting ready for work and in the heat of the moment of just purely angry she has said " if mom falls in this apartment and dies I am blaming you 100 %." Harsh huh?  

 I understand that it was because she was mad , and we normally say things that we don't mean, when we get mad, but I just don't know what to do, it took me a while to calm down before work , because I couldn't tell if I was upset, or pissed off. 

I just don't want to live in fear of my family  hating me more that mom might end up getting worse because I know that they will put all the blame on me over every little thing possible. 

Am I over reacting ? Am I looking into this more then I should be? Thoughts please.