As a PP stated, the BF should not have asked if the GF could stay. He should have presented it as a fait accompli - "GF needs to stay another day. She's in too much pain to drive home." It îs inconceivable to me that BF's mom essentially threw her out.
Previous communication misunderstandings not withstanding, the meaning of this was perfectly clear. "I was forced to invite you. You served your purpose (BF stayed home for the party), now get out."
I'm also not going to play Monday morning quarterback about how the GF should have been more proactive about guarding her health, or about how she should have shared more about her disability, because it doesn't really matter.
Her BF failed to advocate for her effectively, and his mother was overly familiar and nosy to boot. I'd never go back either, and I'd be seriously reconsidering the BF, too.
Except that it does matter. I'm all for showing sympathy to the OP, but I do think it makes a difference in giving her some perspective and not just validating her feelings. Yes, she has a right to be upset. She was
treated poorly. Her feelings are
valid. But, assuming that she wants to stay with her boyfriend, how does she move forward? Always avoid his family? Perhaps...but there could be some perspective too. Why was the mother overly familiar? Well, it could be that she thought the first visit was something other than what the OP thought. There's room for understanding there.
Why was she nosy about the disability? Who knows. I guess one reason could be to discriminate against her when she found out it couldn't be fixed by surgery, but could not another reason be so that she could better understand the needs of her guest? I'm sorry, but I don't think it's fair for the OP to say "I don't want to talk about my disability, it's private and none of your business" and then turn around and say "she made me sit for too long and then didn't understand why I stayed in bed for two days." There's a balance there. She has to advocate for herself, because even though the BF should have also done it, she needs to not rely on him when it comes to her health.
I think that understanding behavior is important and I also think understanding what you (general) can do better the next time you're faced with a similar situation is also important. Personally, I think it's a bit depressing to be told that I do everything perfectly, so that hard and horrible sitations such as this one are completely out of my control. I'd much rather know that there is something
I can do prevent this from happening in the future. And encouraging her to be more proactive about her health and asking her to see where some misunderstanding and miscommunication may have been does that.