modal verbs - 'Should have' in a factual sense

From Dickens:

‘We all believe, up at the Lodge, Rachael, that he will be freed from suspicion, sooner or later.’

‘The better I know it to be so believed there, my dear,’ said Rachael, ‘and the kinder I feel it that you come away from there, purposely to comfort me, and keep me company, and be seen wi’ me when I am not yet free from all suspicion myself, the more grieved I am that I should ever have spoken those mistrusting words to the young lady. And yet I— ’

We usually use should have to say that something was not done, despite being desirable. But in this example, the mistrusting words were indeed spoken (earlier in the book). How would one explain the use of the should have construction then?

Would the following be fully equivalent to the above quote:

‘We all believe, up at the Lodge, Rachael, that he will be freed from suspicion, sooner or later.’

‘The better I know it to be so believed there, my dear,’ said Rachael, ‘and the kinder I feel it that you come away from there, purposely to comfort me, and keep me company, and be seen wi’ me when I am not yet free from all suspicion myself, the more grieved I am that I have spoken those mistrusting words to the young lady. And yet I— ’

Answer

You are right it means nearly the same as:

the more grieved I am that I have spoken those mistrusting words

But saying

the more grieved I am that I should ever have spoken those mistrusting words

intensifies the feeling of grief at the mere thought of having said those words.

This use of should is called the "putative should". It does not carry any sense of obligation but helps reinforce the idea of regret Rachel now feels at having said those words.
It can be found after constructions expressing regret or surprise like:

• It's a pity (you should leave so early).


• I'm surprised (you should talk to him).

It is quite a literary turn of phrase and more likely to be found in classical literature than in everyday conversation. Although it is not uncommon for people to say things like:

Funny you should say this...

and I have found quite a few contemporary examples on this grammar blog