Life advice

Good advice, but whether she will be able to follow it remains to be seen. Can you offer her support or point her towards support groups?
I think the one thing I would hesitate about is the anti depressants. She is depressed for a reason and addressing that reason seems preferable to just seeking help in medication.
Therapy or counselling should do more for her self esteem as would the companionship of friends. If she is a church-goer, her vicar/minister/priest would certainly be someone to turn to.
However I question where CAB come in, unless there are financial issues involved.
You have made a good start with her, can you include her in the odd coffee/lunch/tea at a Garden Centre (maybe not earth shattering, but most of us enjoy those!)
What you describe is sadly very very common among women of our age.
(I don't think "daring" comes into it, it was a kind and caring response to her situation)

I have a very good friend of many years in a very similar situation and after 50 years of marriage seems content with her lot which goes to show we are all very different.She has never said a word against him.They live very frugally compared to most and she never carries any money and when we have been out with them she never looks in shops , expresses any interest in clothes and never wears any makeup. For a few years after his retirement they travelled quite a lot and always flew business class but that has stopped now and they do not holiday anymore.I do wonder now and again what would happen if he "was the first to go" but suspect nothing would change. Her younger sister is so different you would think they had a different upbringing.I think your friend was asking for advice but I would be very loathe to give it.

You say she is a "long standing friend" but go on to say "no-one visits."
Do you not visit her? Does she visit you? (Clearly she does, as you say she drove off, so she has enough independence to drive to friends)
Who is this "friend" of her DH?
By using the word "dare" are you suggesting that she is physically prevented from contact with other people? Surely her grown -up daughters must have some idea of what is going on?

I would be holding my tongue, by voicing what you think she may hold it against you at a later date.

Ex was very bullying and controlling, I could feel myself sliding down into just the same state. Looking back, what worried me more than absolutely anything was - with no money, where would I go? I knew that I didn't want my DD growing up thinking that my situation was normal.

I was helped out by a friend who said that I could stay with her, if I ever left. I did, for seven months. She helped me to get back on my feet.

I suppose the best thing you could do to help was to find out where she could go to, I'm sure that is the single thing that stops most people from leaving.

Yes, that's what I was thinking during Unforgotten last night - that poor woman is trapped with her bullying despot of a husband because she's got nowhere to go and anyway has had the stuffing knocked out of her.

I think the advice about counselling is good, but obviously only if your friend wants if, LuckyDucky. It might give her the opportunity to see a light at the end of the tunnel, so to speak

She and her husband have had a talk with a physiatrist friend. Situation is calming down. Both are talking .

When she was upset words tumbled out of her mouth, I didn't want to pick holes in what she was saying. Not good.

Holding her hand and supplying tissues seemed sufficient.