What's the most difficult decision Marjane has to make specifically and why?

I believe that Marjane's most difficult decision is walking away from her faith. Banishing God from her life would leave her with nothing, Islam is an integral part of the culture. Her final break with her faith came after her Uncle Anoosh's unwarranted execution. None-the-less, that break left her completely isolated and alone. Knowing what this decision would ultimately cost..... I see it as the most difficult decision she'd make.