Your health both mentally an physically comes first, personally I'd rather someone be off rather than come to work A sick an pass it to me or B come in totally stressed/anxious an it ends with a argument or nothing gets done, or the work gets badly affected
Remember places will replace you within a week so take care of yourself first, your job isn't worth sacrificing your health over, is it worth talking to management about how your mentally struggling with her? Or are you able to talk to her an explain what's going on? Sometimes people don't realise how much they push an if you go with it they keep pushing, if it's brought up then maybe she will realise an calm down, so if you can't talk to her then let someone know, most workplaces have (or should) have mental health practices in place for employees