'Should have' in a factual sense

Question

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 1

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

Answer 2

Interesting question!

Your interpretation is correct. She is affirming that she spoke those words, and expressing her grief over having done so. Note that ever does not need to be removed: "that I ever have spoken" is correct.

This is part of the slightly archaic English pattern of using "should ever have" in a that-clause to indicate surprise, indignation, sadness, or other emotion about something that did in fact happen. (See examples here and here.) This is sometimes expressed with "should have ever" or simply "should have." This usage has somewhat fallen out of modern English, especially in American English, which might be why it seemed strange to you.

As a side note, you did well to understand the meaning from context despite the grammatical confusion. Keeping context in mind is especially important with older texts, since constructions that were common then might be unfamiliar to present-day English speakers.