I too was part of the sandwich generation. My mom was officially dx with ALZ when my D was 12 and my dad had been chronically ill for 30 years at that point as well. The second my D was on the bus I was helping with caregiving until it was time for pick up. They my H was forced to make a job change out of state, I stayed back a year for D to graduate HS and to get a plan in place for my parents. Then I was long distance caregiving until they both passed two years later. Super hard, super stressful and I know my D was like yours, in not wanting to add any stress to my plate. I worried about her a lot and guilty about not being 100% present.
We have a whole thread about it here if you think it could be helpful: Parents Caring for Parents Support Thread (Part 2)