Please don't blame yourself for not second-guessing your
Mother's decision to go to the bathroom unassisted. Wouldn't you want to do the same? It's only natural to want to maintain that piece of self-dignity eventhough she probably knew better. It was her choice and you respected it as you should have.
I'm sorry you feel astranged from your siblings. You can try
to heal the rift but know that you can chose to make other friends who truly care about you your family too.
Love yourself as your Mother would want you to do!
Annie