"From the information we have, they didn't do that. And Rachel sound like she would have appreciated some help but no one even asked."
I maybe missed where Rachel asked for help and was denied? If she asked and her friends said, "no way! You are on your own!" I would share the outrage. But if, instead, as the OP said Rachel downplays her disability, I would assume the friends had no idea she was upset or needed help.
Actually, prior to the second outing, we're told that "Rachel apologised if she didn't make clear the effects of her illness and said her vision and balance were still bad. Joanne seemed to accept this."
And then, while at the movie theater during the second outing, Rachel twice made it clear that she could not handle the stairs:
"Rachel suggests getting drinks. Joanne says no, let's find our seats first. Rachel says "I won't be able to get back up again and then down again."
Joanne says no problem. They find their seats (walking down a stack of stairs, Rachel holding on for dear life).
Joanne then says "let's go back up and get drinks and stuff." Rachel again says she can't because the stairs were hard the first time around
. Joanne goes anyway and comes back an hour and a half later with the rest of the group. No drinks for Rachel and just hands her back her money and says "sorry I couldn't carry anymore".
So yeah, Rachel did attempt to make it clear that she was having trouble. Her "friends" didn't seem to care. Heck, they couldn't even be bothered to make sure she was with them when they left the theater! Instead, *knowing* she had trouble with the stairs, they ran out ahead, didn't check to see if she needed help or was even with them, and headed off to a bar without telling her. That's pretty inconsiderate in my book.