>> Do you know much about her past life? She always had boyfriends, in her 20s she dated someone for like 7 years, she had a miscarriage in her 20s, after dropping out of college she moved from city to city (3 hops total) probably dumping one person along the way. Her mother told me that she was never the same after her divorce. She got knocked up on a first date and then they tried to get serious, but he just cheated on her the whole time and acted aggressive.
You need to go deeper into the above and learn more about her sex life in these relationships. Particularly her "abusive" marriage.
I want to commend you for your effort to resolve these issue in a healthy way and to really get to the bottom of what your wife's experience of this relationship and the problems look like. I just want to add another perspective that may help in the grand scheme of figuring things out.
Understand that women and men are very different in their relationship with their own sexuality. Thus far the book Come As You Are by Emily Nagoski, is the only piece of literature I've read that truly captures the magnitude of these differences and the corresponding impact on women's sexuality. One critical point the author makes is to clarify that women's sexuality is heavily defined by social constructs and heavily influenced by context.
Men, way less so. This simple point gives so much insight into issues ranging from women being so negatively affected by body image pressures from advertising or women viewing sex as bad as a result of an ultra conservative religious community or women feeling coerced to "give" their partners sex. Moreover, understanding that women's sexuality relies heavily on context also helps to explain why a light butt slap could get her wild and turned on at the beginning of the relationship but result in her turning into the dragon lady a couple years down the line when she has a baby. Historically, women's sexuality has been defined based on the understanding of male sexuality, a much simpler and straight forward construct, which has led to us women having to deal with men (and women) viewing us as "omg why she gotta be so complicated and make things so difficult".
Therefore it is not nearly as simple as: if she doesn't want to have sex with you it must be because she is not really in love with you.
More things to consider:
1. Considering that women's sexuality is heavily defined by social constructs, it would behoove you to get a better understanding of your wife's childhood and early sexual experiences that would have defined her attitude toward sex. Not to mention her past relationship(s).
I'll give you a simple example of how this has helped myself/my partner - In the past I responded very negatively when my partner attempted to flirt with me by pretending I'm a stranger he's calling to (eg if we're out and he makes whistling noises or flirty comments when he catches my eye/ear if we are physically distanced from each other). I could not verbalize or understand why it enraged me. Only through conversation about my childhood did it come to light how negatively catcalling affected me. Over this side it is the norm and it can become very aggressive when it is done by males in groups. I can recall feeling the need to protect my older sister and feeling her shame from the verbal assaults of catcallers from the age of 9. This was the source of my deep-seated anger towards my partner's innocent attempts at flirting, and it contributed to a bit of an overwhelming need to hold hands with my partner in public. I felt safer when he held my hands in public as the likelihood of catcalling would be slim to none. So when he was concerned that I got annoyed if he didn't hold my hand because I wanted him to publicly display his affection/our intimacy, it was really because of my anxiety from potential catcallers and the nasty feelings surrounding bad experiences from childhood.
2. Sexual response relies on a dual response as opposed to an 'I am in the mood or not' approach. While this is applicable to both men and women, because women are generally more sensitive to context there are a lot more considerations that make up their dual response construct. The dual response: 1) accelerator/ excitor, 2) brake/inhibitor. The accelerator is the body's turn on response to anything around us that we deem sexually relevant; brake is the turn off response to anything around us that says we shouldn't be in the mood right now. Most of us women are smack dab in the middle of both of these however some of us are outliers for one or both of these responses. For example some women have very sensitive brakes so discomfort with their own body will be an inhibitor to them being able to have sex especially with the lights on, an example of sensitive accelerator is getting easily turned on by certain scents or a visual that may seem sexually irrelevant to others. Or for some women knowing their children are awake and around is a major brake whereas some women can have an exciting romp once the kids are taken care of and the door is locked. Or for some women the idea of sex in public is a great accelerator, and just hinting at it seductively could turn them on.
3. It is common for women to have very little understanding of (and appreciation for) their bodies. Us women grow up knowing more about what a random penis looks like than our own vaginas. Think about it, men's sexual apparatus is right there, easy to see and operate. If a woman does not consciously sit back in front of a mirror, spread her legs and examine her vulva, she ain't gonna know what the thing really looks like. Likewise masturbation does not come as naturally to women compared to men. All of this adds up to some of us women not really being in tune with our bodies and not being able to communicate what we need. We have this idea in our heads of the end goal but no clue as to how to get there.
For a long time I wanted this sensual sexual experience where I trust my partner fully, and I savor his caresses, his whispers in my ear of how much he wants to make love to me, where I enjoy his rough hands all over me, sweet slow music in the background, his warm breath on my ***** lips right before he kisses them hungrily, me cumming all over his **** while I look him in the eyes and ride him slowly. NEVER EVER HAPPENED. We could never get to that point because I was always rushing into things. I felt pressured to get wet and horny quickly because I was overly conscious about how long it took for me to get there (example of a sexual brake) compared to my partner whose **** was always stiff and ready (the result of a social construct defined based on men's sexuality - something's wrong with the female who's not instantly ready and willing for her male partner). The result was I usually did not get wet but went ahead and had sex anyways which often resulted in me experiencing some pain or me not being super horny and into it, or a combination of both.
So let's say the situation above is the norm for a woman in that her sexual experiences with her partner frequently mirror the above or something similar. While this woman feels a deep need to have fulfilling sex, her own poor understanding of her body, backed by negative sexual myths only serve to hinder her ability to truly enjoy sex. Add to that her having sensitive brakes and zero understanding of how context affects her sexual desire. Plus a husband who is frustrated that she's not in the mood as much as he and when she is, she doesn't seem to find it as pleasurable as he. The result is a woman who is very confused about why sex doesn't just happen naturally or as amazingly as she truly wishes it were. Because this is all she's ever known about sex, she wonders if something wrong with her or could it be that something is wrong with her partner? Even if she considers that something is wrong with her, where does she begin to figure it out? This is often what leads to women suggesting that ok maybe if he offered more domestic help, maybe if he lost weight, maybe if he did this differently or that differently or did this for me or something else at this time.
She simply cannot comprehend that her understanding of her sexuality is severely limited and based on erroneous assumptions going wayyyy back. She is not able to recognize how all of this adds us to a self-defeating approach to sex, and years of poor sex that has solidified in her mind that it's just not worth the hassle. Or that sex is all about her husband's pleasure. Or that amazing sex is for other couples.
Edited to add: #4 - There's a lot more to sex than penetration.