PilgrimQuill
There's more to this than meets the eye. Two things spring to mind - firstly, she is single and 35, could there be a relationship issue or a health worry which is driving the anger? Secondly, such targeted yet diverse comments sound like the responses to an online questionnaire which she filled in for some reason unconnected with her mother. For a daughter to employ her mother in the first place there has to be a good relationship at the bottom of everything.
I think I would tell her I had seen it and been terribly hurt by it and see what the underlying explanation was before doing anything else.
Then offer to leave the job if that seems like a good idea and follow the advice already given to take up other pursuits and enjoy life elsewhere.
I'm with PQ on this. You need to be honest with your daughter. I would wait till the hurt and anger have settled a bit, and, in a calm and non-confrontational way, ask her about the note. I think I would let her know - without using the self-pity card of "how could you do this to me" or "you know I'm having a difficult time at the moment because..." or similar - that you were quite upset about finding this note, and perhaps that the pair of you need to sort out why she feels that way.
You have nothing to lose by resigning from your job assuming you have some sort of pension, and at 70+ you should be able to do more of what makes you happy - even if that means re-evaluating the rest of your life and relationships. Be assertive (not aggressive) and stand up for yourself, because it sounds as if no-one else will!
Having said that, I am a Grumpy Old Woman, "matriarch" of my family, the most pig-headed and obstinate (but rivalled by my 3 offspring), and someone who likes to have the air cleared in a non-confrontational and rational way so that I know exactly where I stand in relationships! So my thoughts on this matter may not be the most constructive....