There is a strong feeling in this story, of slowness and laziness and tiredness all combined. It makes it rather eery on some level, because of the frightening tension between the lounging laziness of Henna's yawn and the exhaustion that threatens her patients but only kills her. It acts as a very nice counterpoint to the life-and-death theme prevalent in Briar's Book.
Another thing I like about this story is how it fits in with the idea of mages in general and healers in particular, as set up in the books. That power has its limitations, that fighting nature will get you killed. This must be especially true of healers like Henna who use the magic that is their own life force to strengthen and hold the lives of others. The imagery you used, with Henna pouring a bloodlike syrop from her body to her patient's, serves to strengthen this notion.
Your descriptions are very strong, especially those pertaining to people's stances and movement. Without once describing a character's appearance, you still manage to evoke a strong mental image of the setting and events. For a very small scene, you manage to turn this story into something both significant and memorable -- a portrait that lingers in the reader's mind. Well done.

Wow. The atmosphere here was thick, laden down with a sleepless, yet dreamlike quality which was perfect for it. You've captured the soul of an exhausted insomniac. Just one more...and another...another...other...
When Henna hit the floor, I'm sure I heard it echo.
One little, nit-picky type thing: "Covering her mouth automatically polite, she yawned and the other arm reached high above in a luxurious stretch."
Covering her mouth automatically polite? It sounds like you've gone overboard with the word ecconomy, or the punctuation ecconomy, or /something/. She could cover her mouth, with automatic politeness, or she could cover her mouth, automatically polite. Note the comma.
But, if that's the only thing I can critique in a story, you've done brilliantly.
Oh, yes. You have.