Hey Griffin,
Ok,
Protestant is a hard one - (for me especially). Episc & Baptists; you can always get them music and make them happy ;). I take issue with the protestants' Sola Scriptura doctrine especially (as much as Catholics were wrong to sell salvation, protestantism hasn't really righted all the wrongs that the 5 Pillars are supposed to)- Sola Scripture is, roughly, the idea that holy books are to be the law of the religion, and interpretations are suspect. Yet Sola Fide, the other prime protesant rule, says faith alone saves you - not works. Sola Fide doesn't reconcile if you a) believe the bible is the only law or literal law, - and b) read Matthew 25:31 through about 46 to see that Doing Good Works is absolutely essential to performing the essence of 'good' and getting the fastpass to the Disneyland Heaven Adventure.
Sorry, I digress, sorry... Gift! yes, well:
Every pastor needs vestments. They are damn expensive and ,well, what good pastor is secretly a stock broker, right?? (A good alb alone runs about 100 bucks!) So vestments, or a gift certificate for Kaufers.com at the bare minimum are good. You could also get a liturgical book, like 'Pastoral Care of the Sick' (depressing but perhaps useful if she somehow doesn't already have one).
But then you're in danger of just getting a gift for the sake of getting a gift. Give your sis something for HER, from the heart, and everybody wins.
A thought: being as she's working the VA (damn hard job to do btw, send her kudos for that choice alone), a selection of warrior's prayers might be fitting... or even something like a piece of art with proper soldiers-in-mind inspiring words.
The soldiers of old (I mean, like, Crusades-era old) used to inscribe Loricas on their shields - little songs/prayers/chants to recite before battle. Soldiers recovering in VA hospitals are in many ways 'battling' still, each day they try and heal: A lorica-inscribed shield for her office, (or even a customized plexi/clear clipboard? to take on rounds?) with a lorica printed on it would be a thoughtful way to go, if I were in your shoes.
St Patric's Lorica was/is particularly well known as a soldier's incantation. http://www.ewtn.com/Devotionals/prayers/patrick.htm
Note; some pastors will frown on it, as incantations are, to some eyes, spells/enchantments... To them I say: prayers are as well. So are Hymns. And no woman or man of the cloth should have shame in singing hymns. And besides, The Lorica of St Patrick was made into a hymn, conveniently enough.
But go from the heart. It doesn't have to be a present catering to her profession/calling. It can just be something for Your Sis.