Perhaps everyone she knew before now remembers her even more, thus guiding them back to her, meaning Legacies will feature every applicable Originals and Vampire Diaries character that’s still living.
Okay, so that’s far more optimistic than realistic, but still.
On the flip side, there are lots of Originals characters who could show up to save Hayley from her inter dimensional woes before it’s too late, although the same memory-related questions are held for them.