I want to express my condolences for the loss of your brother
. I'm so sorry. This is certainly not a time for anyone to be treating you so poorly.... not that there is a good time. But especially now is when others, no matter who they are, should certainly be showing sensitivity and caring.
As for your girlfriend, I agree with the first sentence of your post. I also think that if your friends and family (more than a person or 2) are thinking it too... that seems to add weight to the validity of it. It does sound very confusing for you, because she seems okay and then 'switches again'. This switching reminds me of people I've known. There are some people who place themselves first, no matter what. Some see things, situations, and people, as "all good" or "all bad", and there is no middle ground. Not sure, but the way you described her made me think of this.
This is definitely a particularly cruel time for her to turn on you. It makes no sense. I think it must be very
difficult to be with someone who consistently confuses you, and has a different reality than you. You said you feel crazy because her reality is different, which is also called 'gaslighting'. It's abusive. You've been in bed for a week
... I think that says a whole lot right there. You deserve a relationship where you are respected and loved and cared for. This doesn't sound like it is, I'm sorry to say. I know you've invested a lot here, and that just goes to show what a loyal person you are.
Please take care of yourself... you deserve it