In the episode where Glory rips off a wall and finds Dawn and knows she is the key. Buffy and Dawn run out of the dorm room. Dawn goes, "I can't anymore," so Buffy carries her!

If you look closly, when she picks her up and starts to run, her hair is covering her whole face and you can only see Dawn in her arms. You can tell she (the stunt double) is way taller than Dawn. But when Buffy puts Dawn down, you can see that she is almost the same hight as Dawn and that there would be noway she would have ran carrying her with Dawn near her chest.