My friend (who isn't scared easily) pointed out that he was never upset by the Alma appearances because she never directly attacks you. But for me, just having her suddenly appear is enough to spook me.
Case in point... (spoilers if you like to be scared?)
There was this one point, maybe halfway through the game, where you're crawling through an air duct, and your flashlight flickers, and the radio makes that telltale crackling. Then suddenly you're plunged into darkness. The flashlight flickers back on, and Alma is crawling really fast towards you, and the music makes a sudden crescendo of sharp dissonance.
I screamed like a girl and pushed myself away from the computer so fast that my headphones were yanked from my head. Never played past that point, partly because I forgot to rescue the savegames before doing a reformat.