My own sister is fighting for my property, and our relationship is getting worse, but after all, I only have one sister. How to face it in the future?

Let's split it in half. You shouldn't use it, and neither should your sister. If you want a big house, you must take less other properties, or use the difference between the current house price and the big house and the small house to compensate and find a lawyer to deal with it. No one suffers, and no one takes advantage.