Responses
That would be counterproductive. She's trying to strengthen the relationship between the Sun and the Sand. If she sent one of her people to do it, it would only create a relationship between the Rain and Sand. Plus, there's also the possibility that if she did that, it would ruin all ties with the Sand because the Sand would think they were being pitied by the Sun.
Why does Nike have to do everything her self? Can't she ask one of her sisters to go to the sand country. I mean she isn't the only who can call rain.