Colour blindness is rare for women, but surprisingly common in men, however there are steps that can reduce the effects while editing images. Those images your sister had printed were probably corrected by the lab if you didn't supply them with specific instructions, but that simply means you gave up control and left it to somebody else.

Displays change over time and their performance steadily deteriorates until they are effectively useless for accurately judging colours. The act of hardware calibration and profiling keeps them within a close tolerance during the useful lifetime of the display and also tells you when the display really needs to be replaced. If you stick with industry standard settings and edit your images in a suitable work area your images will appear remarkably consistent year after year, even if you change display, computers and operating systems.

That part I mentioned about the suitable work area is often underestimated. If you are sitting in a room with yellow walls, green curtains and mixed lighting you are making life very complicated. You really want to keep the work area nice and neutral.