My mother pretends to be asleep and then jumps as if startled when we walk by. This happens 40 or 50 times per day. Is this normal?

My mom does the same thing. 85 years old. Dr. diagnosed her with mild Alzheimers and I think she has some Dementia. Hard to tell if she really forgets, is faking or wants attention. Having had her formally tested, but I 'll leave that for another discussion. She will be in her room and we go in and she will look straight at us. When we call out to her she acts startled. But like I said, with everything she does its hard to tell if its real, or just wants attention. But you said it's so obvious she's faking. I see where it would be frustrating. Hang in there.