Holly Potter was the older sister of Harry Potter. Voldemort never tried to kill her. He didn't even pose a threat to her. She presumes he doesn't even know she exists. Which also means, most of the wizarding world doesn't know who she is. Naturally, having Harry Potter as a little brother means she is more than often the second, or third, or maybe even last choice. Maybe that's not the case when she becomes best friends with Fred Weasley