I think you might be unfair to her.

I know several people with MS, one person with Lupus, etc. These diagnoses are life changing, plus, there are many different approaches to try. In the case of MS, life in a wheelchair might be on the not-so-distant horizon. Getting that dx is a truly challenging experience because the prospect of limitations clashes with the hopes and dreams that had been developed before the illness was diagnosed.

Those two things that you are comparing as if there were on the same level - your anxieties and insecurities and her newly dx'd autoimmune disorder. For the purposes of the discussion, let me use the example of MS.

Most people have insecurities. A whole lot of folks have anxieties. One does not die from them, does not become bedridden and does not need a service dog.

Your gf, with MS, might end up in a wheelchair, might end up unable to mother children, and might eventually need a specially trainer service dog. Her limitations would have to inform academic and professional choices, affect travel, etc.

It is a major major battle. And you are using her as a barometer of your good-enough-ness (if she pulls away, you interpret that gesture as a negative assessment of yourself and that you are not good enough). It is too much to put on a person who was recently diagnosed with MS. Not only does she need to think of what will happen to her, she has to make sure that your fragile psyche is not injured by her less-than-enthusiastic reaction. In other words, you are asking her to perform in a role that is simply way too demanding, and asking her to do that is unfair to her.

If she smokes weed, it might be to lessen the pain. Smoking weed is common among MS sufferers. And/or she might like the high as it lets her escape thinking about the crushing diagnosis.

Going back to the topic of the thread - you might be misinterpreting her signals. She may not have the guts to tell you outright that your comparing your insecurities and her MS is outrageous (if that is what you verbalized to her), that your attempts at roughhousing manifest your inability to pick up on subtle cues of her distress and despair - cues that should have demonstrated that roughhousing is not appropriate, but say, putting some beautiful and somewhat sad music on is appropriate, or, giving her a very gentle hug WITHOUT EXPECTING RECIPROCATION is appropriate, but not roughhousing, because roughhousing is done with an expectation of reciprocation, and she does not feel like reciprocating but does not want to hurt your feelings so she does not say it straight.

OK, I realize that it is harsh, but I am yet to see another post in which insecurities and MS are paired up so nonchalantly. Do you even realize what it is for a young woman to receive a dx that may mean that she would not be able to have children?? What roughhousing are you even talking about?

You wrote "instead of accepting anything" as if:
1) it is no big deal and a piece of cake to accept a diagnosis that radically challenges your plans and dreams, possibly reduces your life expectancy, crushes your hopes for having children one day
2) you of course would easily accept everything.

I am just so appalled. trying not to sound harsh, but, on the other hand, you asked for advice in the last sentence of your post, so here is the advice for you:

Tell her the truth. Tell her that you have no idea what she is going through.

And leave it at that. As a moment of truth. Without expectations, communications skills, direct or indirect but just as a moment of truth. She might appreciate it, and at least she won't be annoyed the way she is annoyed when you initiate roughhousing against the backdrop of what must have been huge neon-color letters that spell "LEAVE ME ALONE TO LICK MY WOUNDS AND DO NOT RUB SALT INTO THEM".