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Thank you.
Hopefully, someday, if and when her illness is managed better, and her grief is being dealt with, things can mend.  It will look different, but I still hope something can be salvaged.  There is a really good person under all her challenges; I've seen that person and hope to be involved on a different level with her.
Meanwhile, I plough on ahead.... the difference being I refuse to be her target of choice anymore.

Thanks so much for the response!  (Fidelia isn't my real name, nor even close really.  Just liked the sound of it.)  The debt was racked up on the joint account so, sadly, I am indeed responsible....but I'm working on it and making progress.
I work at the opposite age extreme to your former job as I now work in a long-term care home.  I genuinely do like it there; it satisfies my soul.

I expect that one of the reasons my youngest is so angry is that, on some level she also now realizes that the net beneath her tightrope has been removed, so she is frightened.  Will she ever come around?  Who can tell.  I hope so, but won't hold my breath.

Sigh.

First of all, what a relief to find this place.  I had no idea such a forum existed and found it by looking up "What to do when your child hates you."  It grieves me that I'm not alone; that so many others are experiencing similar pain, but I am also comforted in that this says I'm not alone; somebody(ies) understand.
Here's the Cole's Notes version of where I am:
I'm 62 years old.  I was widowed very suddenly and unexpectedly last August.  DH and I had 3 children.  A son, from my first marriage, and two daughters of ours.  There were also 2 sons from his first marriage which is a whole other mess for another time perhaps.
DH suffered from bi-polar disorder which, after many years and medication trials (I thought, as did our doctor) was under control.  One of the common manifestations of the 'manic phase' is out-of-control spending.  I had NO IDEA it was happening, and take full responsibility for not having been more vigilant re: our finances.  However, DH always assured me things were fine, and I took him at his word.  Imagine then, my shock and horror to find that every penny was gone, and a further 61 thousand dollars in debt had been racked up.  In the past 8 months I have managed by going back to work (had been retired), taking on every available overtime hour, and cutting my budget beyond the bone and right into the very marrow, to pay off almost half of that.
Our youngest, who was always a "challenging" child, and also suffers from bi-polar disorder has concluded that I, and I alone, am to blame for, well, everything.  Her father, in her mind, is now Saint Daddy who did no wrong ever.  (DH was, indeed, the "fun parent", and I carried the weight of most of the practicalities.)  Side note: as part of her challenges to us, she once accused her father of being abusive (physical and mental but not I hasten to add sexual), which lead to Family Services removing her from our home.  She was back within a few days.  She made a LOT of questionable friendships and decisions in her teen years, but we were always there to pick her up, give her and her kids a place to live, money, gifts etc.  As it turns out, her dad spent a lot more on her and her children than I knew.  In any case, when he died, that tap was turned off quickly and forcefully. 
I have received several poisonous text messages from her since accusing me of being a bad, distant and neglectful mother and grandmother.  These notes are absolutely viscous towards me, and canonize her dad.  I suspect there is a lot of guilt behind that on the latter part. And so much anger!  I am, as I entitled this, The Target of Choice.  Yes, she is receiving medical attention for her illness, but so far....as was the case with her dad....the results aren't quite as hoped. 
Honestly?  I do NOT need this added stress.  Not at my age.  Not in my financial position.  Not while I'm still adapting to being a widow for crying out loud.  Thus far, whenever I get one of these texts (and there have been several), I do not answer them as I need not attend every argument to which I am invited.  She is utterly convinced that her accusations represent the pure unvarnished Truth.  DH was also like that in his depressive swings...so while I have seen this before (and survived it), I feel like I'm being kicked when I'm down.
Is this all self-pity (another accusation I get) or....  I don't know...what?
Thank you for reading/listening.  It helps just to put it down and out there.