According to the old customs and traditions, relatives who move into a new house always give some daily cooking utensils such as chopsticks, bowls, basins, pots, etc. I personally think you can also buy a set of high-quality tea sets or a set of beautiful bowls and chopsticks for your sister.
Now new houses have formaldehyde and other gases that are harmful to health. You can also give your sister an air purifier, which can purify the air and benefit the health of the family. I think your sister will like it.
You can also see what other household appliances your sister's new home lacks. If the economic scope allows, you can also give your sister the household appliances she needs, such as TVs, refrigerators, etc.
Finally, if you really feel that there is nothing good to give, you can give your sister some financial support, hehe... Usually the economy is tight after the house is renovated, and giving some money will definitely be a timely help for your sister.