Hi Loobylye. I'm in a similar position. I'm 56, single, and after two years working from home, splitting with my partner, children all grown up, and some very serious family issues I had been feeling very much the same as you: old, demotivated, lonely, anxious and scared about a future with no sign of anything positive in it.
So, I made a 'plan' of all the things I would try to improve my life...
I had to admit that I was quite depressed. I've been on anti-depressants for a long while and had nearly weaned myself off them but have increased the dose until I feel better.
I have started to go back onto the office to work (which I was dreading but it's actually been good).
I have got an additional part-time job for a new challenge and to meet some new people. (Not started yet and I'm quite scared but also feel it will be good.) I would have done some voluntary work if I hadn't got a job.
Me and my ex are giving things another go...
I've just filled my bedroom with plants...
My advice to you, really, would be similarly make a plan, throw yourself into some things. There has to be something to motivate and engage you in everyday life, as well as something on the horizon to look forward to.
If you've been through a lot and are 'starting again' then, of course, it's scary and it is harder to make a new life and friends as you get older. But your life's definitely not over!
(Your sister doesn't sound at all supportive.)
I hope you sort things out and start to feel better soon.