I think my wife is having a mid-life crisis

I found out six weeks ago that her feelings have changed and she's not sure about us. Apparently she shut down because she tired of my overreactions to minor situations and now feels empty. I have been diagnosed with anxiety disorder and do overreact on occasion, although she admits that it's always over and forgotten after a couple minutes.
Anyway, we've been together more than 20 years (she's 42 but still gets carded for being under 21 frequently) and this has always been the case. While I'm not discounting the impact prolonged behavior like that can have, she's also so afraid of aging and said so many times over the last two years that she had nothing to do anymore and would shoot herself in the head, that I can't help but think that a mid-life crisis is also part of this.
Her solution a few months back was have a couple of friends (both guys about 10 years younger) over every Saturday night through most of the day Sunday and drink like crazy. This was about four months straight.
As part of our trying to work things out now we're going to counseling and she's cut back a little on the stayovers, which I think are just a way of avoiding things and boosting her ego that she's still desirable.
A few people have suggested mid-life crisis and she doesn't want to consider that idea. Yesterday, she brought it up and started talking so I thought it was a time to produce some materials on mid-life crisis for her to consider as a possibility. I tried to present it calmly and without judgment, but she read it and blew up. She said she saw herself in there, but then absolutely refused to believe she's going through a mid-life crisis.
I don't know what to do now. I'm convinced more than ever she's in a mid-life crisis but nothing can be done if she's not willing to accept it.