Struggling to meet 1-to-1

I’m supposed to meet with a teacher for coursework since I’ve been struggling to finish it due to my mental health. However we didn’t decide on a date yet and she suggested today or tomorrow in the morning. But the thing is, I feel nauseous right now and tomorrow in the morning I have a maths class where I’ll be getting a practise test. I’m not sure what to do…

Email your teacher or go and find her today saying that you probably won't be able to meet her today or tomorrow and maybe suggest other times you could meet up.