Parkinsons and related depression and anxiety

I am a recent carer for my Mother in Law who has just been diagnosed with Parkinsons. She will stay with us until she can go home which may be a few weeks or months.
She is currently having her medication tweaked as well as seeing specialists and having a brain scan soon.
Fortunately I can work from home while my husband goes out to work.
My mum in law is extremely anxious, and can’t seem to rationalise anything, waking at 4am every day and turning the 24 hour news channel on, which exacerbates the worry. She is talking a lot about her childhood, and bad things that happened to her.
Are there any tips for helping her to escape this cycle of sadness and/or depression? Every small comment seems to remind her of sad times. It must be exhausting for her, as it is for all her family.

The longer she stays with you the less likely it is for her to go home!

You may well be heading for a dreadful situation, where you have no privacy in your home, no opportunity to go out together, to take holidays.

How to avoid this depends on a number of things.
Does she own or rent her home?
Have over £23,000 in savings?
Does anyone have Power of Attorney - if not deal with this URGENTLY. Do not delay.
How old is MIL, you, husband?
Is your husband an only child?
I know these look random questions, but there is a serious reason for asking each of them.