When the "humane 7" finally graduated high school, they were increasingly puzzled by the lack of responses from colleges, not even rejection letters. Further investigation led to a terrible discovery—the effects of Equestrian magic on a world not made to withstand it were greater than they'd ever anticipated, as the very universe they inhabited seemed to be crumbling around them. Nearby towns were empty ghost towns, as if the people living there had just fallen out of existence, and all evidence pointed towards the same fate soon falling upon the town where Canterlot High was located, though it still stood as the central point of it all, kept stable enough by the portal itself.
Immediately, word was sent to the Equestrian princesses, who offered sanctuary and citizenship to any remaining residents of the human world. By the time the alumni and students of Canterlot High executed their evacuation, many had lost families and friends, as it seemed that those most exposed to Equestrian magic had had more luck in not falling victim to the collapsing world.
There was much shock when the 'humane 7' emerged from the portal as alicorns, but the Princesses were quick to offer them their own royal titles if they so wished. All but one declined. The remaining six, who had all lost the majority of their families to the disaster in home world, wanted only to be allowed time to themselves to grieve and to adjust to their new home.
The citizens of Equestria seemed to have other plans. Whether they were being recognized as their counterparts or as the 'otherworld alicorns,' they were an object of great interest wherever they went. All six ended up going to great lengths to try and differentiate themselves physically from the counterparts in this world, but it was to no avail.
Wherever they went, no matter the fact that they had denied the titles, ponies whispered about them, calling them "the Refugee Princesses."