Dino's in Cleveland Park closed; Dino's Grotto then opened in Shaw. Same owner, slightly different concept, still wine friendly. However, I don't find myself going there very often even though I live in the neighborhood.
For restaurants, Ripple probably has the best list in DC for someone with a disorderly palate (or really for anyone, in my opinion). I believe (but your friend should confirm in advance) that there is also some kind of corkage arrangement for bottles purchased at Weygandt, which is just a block away.
Other restaurants I would suggest that are at least pretty good on both the food and wine list fronts without being insanely expensive include Etto, Red Hen, and Cork. A call in advance might result in some sort of corkage arrangement at these places, but it is unlikely to be free.
If your friend has any interest in a casual but relatively authentic Thai feast and would bring a bottle or two of wine that does not clash with Thai food (I usually choose off-dry Riesling), he/she should check out Thai X-ing, which is very reasonably priced for the amount of food you get and has a corkage policy that is extremely friendly. Two notes of caution. First, if you don't bring your own wine glass, you will be drinking wine out of a water glass (which, given the casual setting, is totally fine). Second, while they try to accommodate allergies, there is no menu - you eat what they are serving to everyone that day. The food is usually good though, and plentiful.
If your friend is looking for something specific food-wise, let me know, but given the discussion so far, this is what came to mind.
For retail, I would recommend Weygandt and MacArthurs first and foremost. Cork Market/Wine Shop and Arrowine (there is now an Arrowine location in DC proper in addition to the one in VA; however, only the one in VA sells the famous cheeses and charcuterie) next. Schneiders and Calvert Woodley also have some good selections.
ETA: There are now two Thai X-ing locations, and I think you can BYO at only one of them. So if going that route, make sure your friend books the right one.
