Have you checked your ammonia levels? When I first got my froggies they did the same thing and it ended up being the ammonia was too high. They also do this zen position. Mine typically dont do it at the top of the tank though. They do it more in the bottom. Like they are standing on their hind legs all chill and relaxed. Its very cool. She could be doing just that only at the top but I would still check the water to be safe.