I don't disagree with anything anyone has said already, but perhaps another perspective on her reaction. It doesn't have to be denial. It could be fear.
If you have been married for 30 years, that places you both in the "older" bracket. What has her life so far been? Does she have a career? A pension? Skills? Has she been a "traditional wife / mother". How does that compare to you? Many women, after 30 years of marriage, their "status" and "identity" can be inextricably linked with being a wife and/or mother in a way that no man could possibly understand because his world is often so much larger. If this is the case, suddenly being something else, something else that you have little or no experience of, can be very frightening. And on a practical level, what will her life then look like - where will she live, what will she live on....
Fear is a numbing for some people, and in particular numbing fear is a more female trait. Many women are brought up to see themselves as attachments to mens lives - fathers, husbands, sometimes even sons and grandsons. We haven't come that far socially that there aren't still all these influences around us whether we adhere to the sterotypes or not - and for many girls growing up in 2022, not all that much has changed since I was growing up in the 60's. On the surface it may look like it has. But pretty much everything around us is a veneer, and it is still a man's world for the vast majority. It may - may - be easier to break out of that mould, but that doesn't mean most people do.
So yes, if you must leave then you must leave, and don't go back again. But equally, you can't just walk away that easily, and there will be a lot of things to resolve - things she may be paralysingly scared of. You are both due some happiness, but yours isn't at the expense of hers either, so it isn't as simple as tell her you are walking away. You need very quickly to move on to practical issues about assets and pension and whatever else is necessary to ensure that she can move forward.