Anal rape of a female child 6 years old. is it reasonable for that female to cry later on in her life while thinking about the experience?

Certainly: Such an experience is a form of torture and one that is never forgotten in normal people. It can resurface during what should be pleasurable activities during sex, or just out of nowhere. The difference for some who become healthy survivors is learning with help to get past it. Those who remain victims have not accomplished that goal. You must do the work to get the benefit.