I certainly would remember if someone gave me $100. But you're jumping the gun here. What other instances of “forgetfulness” or confusion or difficulty with normal daily living have you witnessed? Dementia is not only not remembering something, it is much more. If you're concerned, have your mom's PCP administer a basic dementia test. If he/she suspects dementia she would be referred to a neurologist for further evaluation.
She's 90. There's going to be a certain amount of cognitive decline, but forgetting one thing is hardly a diagnosis of dementia. (I'm 59 and can't remember what I had for dinner last night.)
Have her physician check her out if you have any concerns, but forgetting one thing isn't indicative of anything.
Have her physician check her out if you have any concerns, but forgetting one thing isn't indicative of anything.
No worries. It is normal.