I've noticed that as well.
Also, Dasha seems to be wearing the same shorts most of the time.
Keep in mind, that we're watching these people at home, and they change when they come in. It's not uncommon for people to wear the same "House outfit" for a week before washing it. As for the green dress, It's fucking gorgeous on her! She's probably worn it three times, and is doing so because she doesn't have a stockpile of worn, but still clean, clothes hanging in her closet. So she'll wear it a few times, then switch to something else.