My DS was the same (and still is) and only ever did a max 11hr night even after dropping the nap, his nights never extended. I agree that it is probably best just to drop the nap, and we just did a set BT of 7pm and kind of rode out the OT. As Creations said an 11hr full night is likely to make her feel more rested than a shorter night and 20min nap, so if you can't do an early BT then just set it and stick to it and it will eventually work itself out. I found the 5pm hour the worst, when the tiredness would really kick in. We also made him have a "quiet time" of 1hr...so that meant on the couch watching a movie or some other quiet activity.