In New Jersey, my father died and left his house to his second wife. Stated in his will, after she dies, the house goes to my sister. Can the second wife change the will and leave the home to someone else?

If your father died and left the house to his second wife, and then when sh dies, it goes to your sister, then what the second wife got in the will is known as a "life estate" and is not ownership of the property.  She cannot change your father's will, and cannot change the nature of the asset she received.  the life estate is recorded as part of the will and the deed should be changed to the name of your dad's estate, with the life estate to his second wife.  who is the Executor of your dad's will?  the Executor has to do this, and if its the second wife, you may need to intervene to make sure it is handled properly.  Good. luck, and if you think I can help, please call my office.