Dear hayfmr, I tend to agree with Lexie---the best way to let her hit bottom is to get completely out of her way. I understand that you don't know where her bottom is.
I also understand that none of these decisions are easy. Even the most "right" decisions can be the most painful ones to carry out. However, I don't imagine that there is any pain that is worse than what you are already living with right now.
If your life has any value to you--take care of yourself. There is no value in sacrificing your own happiness. You are just as important as she is. What you are doing isn't helping her, anyway.
sincerely, dandylion