You have not asked it. My opinion on all sexual behavior is pretty much this:
As long as two people are consensual and nobody is physically harmed or emotionally violated, to each their own.
I personally don’t like a handful of things and knife play is one of them, along with scat, blood, multiple partners, and I am reluctant about rape fantasy too.
Like I said, I don’t care what other people do, and I don’t judge them. There was a time when half the stuff on my blog that I love now was off-limits to me and I would have entertained multiple partners which now I wouldn’t, so we all ebb and flow and change through time. I just don’t see knife play as being something that will ever appeal to me.
Then again, if she wanted it, I’d do it cause I am a giant vagina over her. So there is that.