I'm not sure if you know this but Sunset is technically an alicorn and with good reason. First, in My past is not today she experiences something of the same as twilight when she became and alicorn. Second in Friendship Games when sunset transforms she gets a horn also. Now some can argue that human twilight also gets a horn and wings so she is an alicorn too, however even though the magic she gathered was from the five elements, they were used for bad intentions, not necessarily bad but like pony twilight said the smallest change can snowball into an avalanche of disaster, while sunset did use it for bad intentions which is why sunset didn't look recognizable in anyway while human twilight does.Third both sunset and pony twilight call upon the elements of harmony but twilight says magic as in her element and sunset say friendship assuming that is the human counterpart of magic says The Brony Notion.
This is evidence that Sunset is technically an alicorn so I would keep that in mind...