It had the added bonus of keeping her perpetually young, since it was her consciousness traveling, not her body. She inhabited the body of whichever version of her existed in her destination. The original didn’t actually leave, but was shoved down and put to sleep. It would wake up when Hermione left and return to normal, assuming the ritual didn’t stress the body so much that it lost the capacity to maintain life. Unless there was someone else on hand to perform a separate ritual to keep the body alive, then the original would die.