50%- 50% owner of property problem

my wife inherited 1/2 of her parents house 4 years ago... her and her sister rented the house to a third party. last year her sister moved into the house after her husband pasted away.. recently we approached her about either buying our house or paying rent.. she refuses to do either.. heaven forbid, what legal recourse do we have?

To bring a partition action and force a court to divide the property. Like King Solomon. That will spur a settlement.