(((((((((((sunny)))))))))))))) I think I can feel your anxiety from here! I recognize the feeling cause I carry it around w/me like a handbag. Wish I could help. Simplistic as it sounds, the ONLY thing that helps me besides meds is deep breathing. 10x, slow, steady with eyes closed.
I think the day spent together w/your daughter, just the two of you, is an excellent plan. I have 2 daughters. Ages 18 & 21. I have done this exact thing several times w/each and it has always been a good thing. I call it a "girls day out". We pick a movie we both want to see, then we eat a nice meal and "chat". After that, we aimlessly shop and giggle a little.
It can't hurt. Amazing how much info you can glean from these casual, unstructured days together.
Also, depending on what the school problem is, the tutor sounds like a good plan. Somebody she likes who comes to your home and quietly helps her. Less pressure than going someplace.

tulips