@Strannger18 said:

We find out that Peter Van Garrett and his son were killed followed by the widow Winship when it becomes apparent that van Garrett married her, making her a possible inheritor. All witnesses to the marriage and any inheritor that stands in The Lady's way are killed. So why wouldn't they automatically get the property since the Van Garretts sold the family the land anyway? His will couldn't change that of the exchange had happened.

The widow Winship did not kill anyone. Lady Van Tassel was not after the land her family once lived on, she wanted ALL Van Garrett's property as an act of revenge.

The change of his will meant that more people than just the Van Garretts had to die.