The blade resembled an 8" long knife. Stupidly I just picked it up and put it on the sideboard. I am now thinking that (she has undiagnosed dementia) when she is in aggressive mode (which is very often) she has access to a weapon. Should I remove the blade from the house and not mention it?
She probably tried to use the scissors to prise something apart and strained the handles off one another. If you can also find out what job it was she wanted done, perhaps you could deal with that too.
I'm sure the half-pair looked very alarming, but it isn't intrinsically more dangerous in the hands of a person with dementia than any other hefty, pointed object. Are you seriously concerned about any risk to either your mother or those around her?
How does your mother show aggression?
I wouldn’t say anything to her about it, but just do what needs to be done.
Someone with dementia is more akin to a toddler. Would you leave a weapon or knife in the reach of a small child?
My FIL's caregiver quit after he cornered her in the kitchen because he forgot who she was. He could have seriously harmed her.
Listen to your intuition.
Are childproof scissors still a thing? I used those in the early grades during art time in school.