Margulies was at a point in her life that we all come to at least once (if not several times), where you really know what’s the right move for yourself, but you feel wrong for wanting it because everyone is suggesting you should do the opposite.
She needed a non-invested party to give some guidance, so Margulies bought a spiritual book, and figured it could help her choose the correct next step.
I have often used the blind-point method myself to make a decision or at least to get some hint of what to do next, and it has never failed to lead me to the choice I’d basically already made, so I can totally understand why Margulies took the note and went ahead and left her life as Nurse Carol behind.