The first thing your wife needs is a psychotherapist, not a doctor. Although she will also need to see a doctor.

A very few -psychiatrists- are primarily interested in psychotherapy, but all psychiatrists are MDs, so it can be a really boon to find a psychiatrist who specializes in therapy, because then they are able to speak intelligently about medical issues as well. This is really hard to find, though.

Anyhow.

It is almost impossible for the average person to find a therapist who isn't a waste of time. Call the largest, most well regarded hospital near you. Explain that you would like to leave a message for the head of their psychiatry department, requesting a referral. Psychiatrists at major hospitals know who the good therapists are, even if they aren't interested in doing therapy themselves.

So when the psychiatrist returns your call (keep your phone with you, you won't be able to call him/her directly, you'll have to just be ready to receive their call whenever they call back in response to your message), explain the situation briefly. Ideally your wife will be nearby, so she can get on the phone if need be. So what you will ask for are 1) three names of top psychotherapists who have experience with sexual dysfunction who are accepting new patients 2) three names of top OBGYNs who have experience with sexual dysfunction who are accepting new patients

Now, especially for psychotherapy, be prepared to pay out of pocket. Uniformly, the best psychotherapists do not accept any kind of insurance. There are very good, complicated reasons for this. Your wife needs the best, so start setting aside LOTS of money.

The OBGYN may accept insurance, but it's more important that wife sees the best (who is also interested in/ familiar with sexual dysfunction) instead of who is covered, who also have an interest in sexual dysfunction, for at least, say, five office visits.

If you want to make progress with this, it will be a huge undertaking. Set aside at least $30,000 for her treatment, if you can.

Ideally your wife will meet with a psychotherapist twice weekly for at least a year.

Listen, even if this problem is 90% medical, the therapy is essential. That's my take.

Also, I suggest you post your situation to /r/deadbedrooms. Most people there are struggling with somewhat different situations than yours, but it's a tight knit community of extremely intelligent, caring adults, most of whom are also married. They may be able to offer you step-by-step advice as you go through this.