Happy house closing and happy birthday to your sister! What an exciting time! 
There have been some great ideas already shared for fun witchy house-welcoming gifts. Does she already have a big stovetop pot? If not, that’s a great gift as a functioning Kitchen Witch’s cauldron. An enchanted stirring spoon is another good tool- which reminds me of @Silverbear’s beautiful DIY Yule Charms! 
Anyways, wishing her all the best with the big move! I’m sure she will be appreciative of any gift you bring to celebrate the special occasions 
