Harry Potter's Twin Sister - Emabookworm

Lillian Rose Potter was the younger twin to Harry. When she was born, she had a lot of power so, Lilly and James called Dumbledor to keep her power hidden and safe. She was staying with her family for Halloween when her parents died protecting her and Harry. She was sent to a different family than Harry because she had to much power that she might have hurt them.

What will happen when these two twins meet each other years later?