One small update: I did make an appointment and told my wife I'd like her to go. It was such a relief to actually make that one small step! She's still uncomfortable about that, so I asked her last night if she'd like to talk about it. I got a "I'm too tired" (which she wasn't, since she went on to discuss a few other things

). So, I feel validated in not waiting, but we'll see if she
will go with me (I told her even the therapist said it wasn't necessary - we could do a one-on-one each first or whatever we'd like to do).
I'm glad that making an appointment helped give you some relief, and hope the therapist can help you find ways to enhance your relationship.
I suspect the "I'm too tired" thing is a short-hand way for her to say a few things:
-"I don't want to deal with this." Facing difficult issues in a relationship is hard, and excuses are easier.
-"I don't feel safe talking about this." If she fears her expressing her emotions may upset you, or result in a change or end to your relationship, she is likely experiencing fear. Fear is a horrible inhibitor to communication, and one that is not easily expressed because saying "I am scared to tell you how I feel" would immediately signal that the speaker was going to say something they feel would result in the above (change in the relationship).
Fear can be created by many things, including:
- past communication issues between the two of you. This could include instances where emotions were expressed, and negative consequences followed, or where threats were made, such as "if I don't get my needs met, I will leave," etc. Or, where her feelings were minimized or not validated, in favor of yours.
- family-of-origin communication problems and punishment. This is common, unfortunately. Things like expressing anger, sadness, or differences of opinion is punished, and so the person learns excuses are easier.
-conflict avoidance personality. This can be caused or exacerbated by past experiences, as well.
-Low self-esteem.
-Societal pressure. The more you post, the more it sounds like your wife may not have ever been particularly sexual. Unfortunately,in our society, that isn't views as "normal," and the pressure to be sexual often causes people to act sexual to secure a mate, because they believe they are "broken," and/or will never find love if they are asexual/not particularly sexual. This can be really difficult to overcome. It is unfair to their partners, and to the person themselves, of course. If you think that you wife may have always lacked an active libido, it's worth doing some research and talking to your therapist about the norm of asexuality, to give you a better idea of how to approach your wife from a supportive place that could benefit you both. It's very possible that, if she is just naturally a less sexual/asexual person, she feels that it is all on her for being "weird," and "broken," and would open up more if she felt that her natural sexuality would be accepted without recrimination.
And some other things I am probably forgetting. You can try helping to remove fear by changing communication patters, and reassuring her without pressure to conform to your desires and needs. It may or may not work, but creating a safe communication space can help.
Let us know how therapy goes!