What I am seeing is a search for some sort of logical construct to help understand, predict, and respond to confusing behavior. Have you heard of the "ring" theory?
https://www.psychologytoday.com/us/blog/promoting-hope-preventing-suicide/201705/ring-theory-helps-us-bring-comfort-in. If not, it may help.
The idea is that the person dealing with huge trauma is in the very center. Their closest family/friends are in ring around that person. Then the people who are a bit further removed (remote family, coworkers, etc.) are in another ring farther out than that. Etc.
The primary rule of the ring theory is that you can send
only support to people further inside the ring than you. When you need support yourself -- because, as you well know, it is really fucking hard to be close to someone dealing with major trauma -- you need to look to rings farther out for that.
IOW, that means you cannot ask the GF for
anything -- not sex, not time, not texts, not attention, etc. The
only questions you can ask right now are "what do you need from me?" or "how can I help you?"
You are legitimately frustrated that she cannot meet your needs right now. Those needs are valid, and the frustration is valid. But
that is what the people farther out on the rings are for. Frustrated you're not having sex? Go out with buddies and vent about how hard it is not to have sex, and that it makes you feel like shit even to complain about it given what she's going through, but dammit, you miss it. Vent to your therapist. Find some online porn. Whatever. Just don't dump it on your GF.
Think of all of these various needs as rocks. Right now, your GF is basically Atlas, holding up the world. Literally all of her energy is used up in not falling apart and in putting one foot in front of the other. If you can find ways to support her, you lift a couple of rocks off of her shoulders. OTOH, if you ask her to understand or meet your own needs, you are piling additional rocks on top of her. Maybe it's a very little rock, sure. But do you really want to be the guy who is making her life even more difficult when she is going through the worst thing she's ever dealt with? And if she's at her limit, even a little rock is all it takes.
From what you've written, she's done a really good job of clearly stating what she can and can't give right now -- in particular, she feels too much stress to want to have sex or think about your relationship right now. That means that you now know, in no uncertain terms, that every time you ask about sex, or suggest that you want sex, or want to know where your relationship is headed, or any of that stuff, you are picking up another rock and setting it on top of her shoulders.
It doesn't really matter whether you see it as a burden, or whether anyone else would, or whether her response is "normal." You know that she sees it as a burden. That is the end of the discussion right there.
Oh, and that kind of shutting down is what happens when you're trying to hold up all those rocks, and every time you talk to a particular person, they end up tossing another pebble on the pile (knowingly or unknowingly). When you're in crisis, you figure out that the fastest way to save yourself is to just not deal with anyone and anything that makes life more difficult -- you triage down to the absolute bare minimum to get through your day and focus instead on people who you
know will be supportive 100% of the time.
If you want to communicate with her more regularly, the solution is pretty clear. If she's limiting communications to people who are lifting rocks and cutting off people who are adding them, be the guy who lifts a rock every time you talk to her, without asking for or expecting a single damn thing in return.
And if you can't be that guy, acknowledge it and let her go radio silent for as long as she needs, so at least you're not making her life harder. (First Rule of Holes: when you're in one, stop digging)
