Try as much as possible to stay out of her way Karen (not always easy when living with a person I know) and if she snaps at you for no reason, can you see yourself going up to her , trying to give her a hug, looking her in the eye and saying "Mom, I'm not the enemy. I'm worried about you too and I wish I knew how to make it easier for you". Sometimes we get bitchy and angry because those feelings can be easier for us to manage in the moment than sadness which can feel more helpless when it already feels that our control has been ripped away.
Try not to yell back (into your pillow is a good place to go scream what you really feel like saying back) since she may be venting in a way by taking out her feelings on you guys but it's not personal against you.
I'm thinking of all of you and I hope things settle out again and also that your Mom is going to be alright.
Hugs kiddo (I mean that in the nicest way) and hang in there. We care a lot about you Karen.