Sounds like something he would write. His novel, The Portrait of a Lady bored me to tears.

What is it? What woman did he mean?

Today, every woman has her elbows on the table between courses. Table etiquette hardly exists any more. It is sad to see these niceties disappearing before our eyes.

This quote is it about pretty me? Yeah... I know it is rude to keep my elbows on the table but i'm so graceful that my simple presence abolishes the violation of this etiquette.

An old etiquette rule forbade eating with elbows on the table. I don't know why. My sister & I had a conversation once, I told her it was rude to have her elbows on the table (I was being sarcastic). She didn't know what I was talking about, she said she'd never heard that rule. She asked why & I was stumped. Maybe it has something to do with keeping the tablecloth clean, although few people use tablecloths these days, just a placemat.
I'm inferring from the quote above that it was rude to have elbows on the table between courses, not just while eating. This quote might once have bee a telling portrait of the character's physical presence. Time has taken the once obvious meaning away.
I imagine the contemporary equivalent would be "She was a woman who, between beers, could be graceful with her feet on the coffee table.

I still don't understand why it is so wrong to place elbows on a table while dining. It isn't harming anyone!

The quote in context : From " The Ambassadors" (1903), book V, ch. II


"Ah because that's the way you strike me." She spoke ever so gently
and as if with all fear of wounding him while she sat partaking of
his bounty. "Aren't you in trouble?"

He felt himself colour at the question, and then hated that--hated
to pass for anything so idiotic as woundable. Woundable by Chad's
lady, in respect to whom he had come out with such a fund of
indifference--was he already at that point? Perversely, none the
less, his pause gave a strange air of truth to her supposition; and
what was he in fact but disconcerted at having struck her just in
the way he had most dreamed of not doing? "I'm not in trouble yet,"
he at last smiled. "I'm not in trouble now."

"Well, I'm always so. But that you sufficiently know." She was a
woman who, between courses, could be graceful with her elbows
on the table. It was a posture unknown to Mrs. Newsome, but it was
easy for a femme du monde. "Yes,I am 'now'!"

"There was a question you put to me," he presently returned, "the
night of Chad's dinner. I didn't answer it then, and it has been
very handsome of you not to have sought an occasion for pressing me
about it since."

http://www.online-literature.com/henry_james/ambassadors/7/

Strether makes this observation about an enchanting femme du monde, the Countess Marie de Vionnet. Placing one’s elbows on the table during dinner is considered a serious breach of etiquette, but, Strether feels, it is the truly classy lady who can do it and get away with it.

That's because "with her elbows on the table" she kept her finger nails out of her mouth by necessity. James himself perhaps, not just his character,
must have believed that "the lesser of the two evils" was the preferable course-- in between courses, of course.
Picking one's teeth could wait until after desert, just before coffee.

;-o

Out of context quotations may sound out of place.

I initially thought it needs the context to appreciate the meaning but after given the context I still don't have much idea what to appreciate about it.. I see that it's still giving us a chance to think and discuss things and it's interesting to me though.

Henry James' writings is a bit difficult for me and I'm not really able to understand that but I think the little earlier part, "his pause gave a strange air of truth to her supposition" would work better as a standalone quote.