My wife has aquired an affinity to knives too. She now expects them to be sharp and will ask me to sharpen them if needed. When she does, I joke that she must be flirting with me.
Seriously, let her know that one is more likey to be cut with a dull knife. Since you don't want that to happen to her she should expect you to keep them sharp as a matter of course. Eventually she will learn to "respect the blade" and treat them all as if they wre razor sharp, until proven otherwise. I guess this is like people with guns treating all firearms they handle as if it were loaded until they prove to themselves that it is not.
Hope it helps.
PS : Maybe then she will have a new way to flirt with you.