How to tell wife she isn't part of my inheritance?

Years ago I was gifted a "shit-ton" worth of stock when my parents both began showing signs of dementia. Cut to this year and both my parents have passed, and I have inherited another large chunk of money in various account types. Long story short, my wife thinks half is hers, and she has "ideas" on how to spend just about all of it. It has never been commingled with joint funds.

So, would I be the asshole if I informed her flat out that my inheritance is mine, not "ours", and although I am willing to indulge her wants, I will be the final authority on how those funds are spent? How would I "break it" to her in the right way? We do have a great marriage and up to this point have never had a serious disagreement revolving around money.