My sister and I own a piece of property . How can I stop her from moving into it?

If you and your siste own the property (joint owners on the deed), you both have a right to possession. You can't stop her from moving in, however you can try buying her interest or if that fails you can seek a legal partition of the property, which in most cases results in a court ordered sale of the property. Once sold the proceeds are divided. Certainly, if you can't live with each other, the cheapest way to deal with this is to work out an agreement with your sister to buy/sell.