Darling, there is nothing you could really do. She was an adult, she made choices...and she did not tell you the extent of what she knew, so you had limited information.
I hear your pain. I refused to see my Mother the time before she finally died (I didn't realise how bad things had gotten either), so she didn't bother telling me when the end was near.
My family's biggest fear was I would consume myself with guilt over something I couldn't change after she died. Please don't you do that either.xx can you talk to your husband or someone close and get this out.....I'm sure they will tell you the same thing.