Great topic!
I've sometimes interpreted it as a grieving woman, but I'm curious to know if anyone here knows about the history of why the Queen of Swords shows up veiled when I haven't noticed such a strong pattern of it amongst the other Queens, artistic/historic styles not withstanding.
What an interesting topic!
Well, Waite, himself certainly agrees with you on the grieving element. He defines her as: "Widowhood, female sadness...absence...mourning, privation, separation."
And, yes, mourning often involved a veil down the back (though, to be fair, veils were very fashionable from the middle ages on up through the Tutor England, so if our queen is more middle ages than 19th century, she might just be fashionable).
Crowley, by the way, also sees this queen as separating from others, and also sees it as a painful process. But he asserts that it's also necessary as it brings clarity. His image does not contain a veil, but it does contain a cut-away-mask. The Queen/Swords is able to cut away others masks and see beneath them. She is all about the independent mind--but this brilliant, independent mind can also get lost in itself, remaining apart from the "real" world. So her separation is in seeing too much, being too clear sighted and affected by what she sees.
Veils were emblems of separation, but being of fabric rather than a wall or door they imply that what it's a shockingly thin line between one side and the other. The HPS' veil, separating natural from supernatural, shows us that they are side-by-side and it's easy to cross from one to there other. I think the Queen/Swords veil, like a nun's veil, signals that our Q/Swords is to be given her space, and approached with respect and gravity, because she is a woman of deep and very important contemplation; she is in a different world than the rest of us, and it is not up to us to cross that thin line and disturb her, but up to her to cross that thin line to join us when she has intelligence to give us.