He has been there for 20 years. Good perspective, thanks.
If after this week it is still impacting other subjects, you will need to reassess.
The difficulties may be due to many students taking precalculus honors and/or getting an A, so the pace is geared toward that.
Definitely better to stick it out if she can, but it’s obviously not worth her mental health. I found the Kahn Academy videos very useful for Calculus. I found that if I watched the video on the topic BEFORE class then I could follow along better and also ask questions during class because I already had some familiarity with the subject. Also, if you can afford to get her a tutor that would probably be a big help, or otherwise maybe the teacher has office hours or there is another student in the class she can form a study group with? Best case is she decides she can do it, next best would be there is someway for her to get into AP Stats. Good luck to her!